#糙集简单

#include<iostream>

using namespace std;

inline int read(){
   int s=0,w=1;
   char ch=getchar();
   while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
   while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
   return s*w;
}


void write(int x) {
     if(x<0) putchar('-'),x=-x;
     if(x>9) write(x/10);
     putchar(x%10+'0');
}

#define N 520

int a[N],c[N],b[N];

string A,B;

int main(){
	cin>>A>>B;
	int len=max(A.length(),B.length());
	for(int i=A.length()-1,j=1;i>=0,j<=A.length();i--,j++)
		a[j]=A[i]-'0';
	for(int i=B.length()-1,j=1;i>=0,j<=B.length();i--,j++)
		b[j]=B[i]-'0';
	for(int i=1;i<=len;i++){
		c[i]+=a[i]+b[i];
		c[i+1]=c[i]/10;
		c[i]=c[i]%10;
	}
	if(c[len+1])
		len++;
	for(int i=len;i>=1;i--)
		cout<<c[i];
	
	return 0;
}

zkw线段树a+b

#include <bits/stdc++.h>
// #include<bits/extc++.h>
#define int long long  //__int128
#define mmst0(x) memset(x, 0, sizeof(x))
#define mmst3f(x) memset(x, 0x3f, sizeof(x))
#define si(x) scanf("%d", &x)  // scanf("%lld",&x) // When define int ll
#define pb(x) emplace_back(x)
#define mkp(x, y) make_pair(x, y)
#define fi first
#define se second
#define YESS printf("Yes\n")
#define NOO printf("No\n")
#define fori(a, b, c, d) for (int a = (b); a <= (c); a += (d))
#define ford(a, b, c, d) for (int a = (b); a >= (c); a -= (d))
using namespace std;
// using namespace __gnu_pbds; // If using pbds don't using std!
using ll = long long;
// typedef long double rld; // use double pls!
using ull = unsigned long long;

const double eps = 1e-6;
const int INF = 0x3f3f3f3f;  // 0x3f3f3f3f3f3f3f3f; // LLINF
const int MAXN = (int)3e5 + 3;

inline char nc() { return getchar(); }
inline int read() {
  int s = 0, w = 1;
  char ch = nc();
  while (!isdigit(ch)) {
    if (ch == '-') w = -1;
    ch = nc();
  }
  while (isdigit(ch)) {
    s = (s << 3) + (s << 1) + (ch ^ 48);
    ch = nc();
  }
  return s * w;
}
// inline int read() {int x;si(x);return x;} // FAKE QUICK READ,JUST FOR DEBUG
inline void read(int &x) {
  char ch = nc();
  x = 0;
  while (!(ch >= '0' && ch <= '9')) ch = nc();
  while (ch >= '0' && ch <= '9') x = (x << 3) + (x << 1) + ch - 48, ch = nc();
}  //
int n, m, ans;
int cnt;
int r, p;
int a[MAXN];
int N;
int tag[MAXN << 1];
vector<int> tr(MAXN << 1);
void build(int n) {
  N = 1 << (__lg(n + 5)) + 1;
  for (int i = 1; i <= n; ++i) tr[i + N] = a[i];
  for (int i = N; i; --i) tr[i] = tr[i << 1] + tr[i << 1 | 1];
}
void add(int u, int d) {
  for (int i = N + u; i; i >>= 1) tr[i] = d;
}
void add(int l, int r, int d) {
  int len = 1, cntl = 0, cntr = 0;
  for (l = N + l - 1, r = N + r + 1; l ^ r ^ 1; l >>= 1, r >>= 1, len <<= 1) {
    tr[l] += d * cntl, tr[r] += d * cntr;
    if (~l & 1) tag[l ^ 1] += d, tr[l ^ 1] += d * len, cntl += len;
    if (r & 1) tag[r ^ 1] += d, tr[r ^ 1] += d * len, cntr += len;
  }
  for (; l; l >>= 1, r >>= 1) {
    tr[l] += d * cntl, tr[r] += d * cntr;
  }
}
int query(int l, int r) {
  int cntl = 0, cntr = 0, len = 1, ans = 0;
  for (l = N + l - 1, r = N + 1 + r; l ^ r ^ 1; l >>= 1, r >>= 1, len <<= 1) {
    if (tag[l]) ans += cntl * tag[l];
    if (tag[r]) ans += cntr * tag[r];
    if (~l & 1) ans += tr[l ^ 1], cntl += len;
    if (r & 1) ans += tr[r ^ 1], cntr += len;
  }
  for (; l; l >>= 1, r >>= 1) {
    ans += cntl * tag[l] + cntr * tag[r];
  }
  return ans;
}

inline void work(signed CASE = 1, bool FINAL_CASE = false) {
  n = 2;
  for (int i = 1; i <= n; i++) a[i] = read();
  build(n);
  cout << query(1, 2);
}
signed main() {
  // ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
  // //freopen(".in", "r", stdin);//freopen(".out", "w", stdout);
  signed T = 1;  //(signed)read();//scanf("%d",&T);//cin>>T;
  for (signed CASE = 1; CASE <= T; CASE++) {  //
    // printf("Case #%d: ",CASE); //printf("Case %d: ",CASE); //printf("Case
    // #%d: \n",CASE); //printf("Case %d: \n",CASE); while(cin>>n) work(n);
    work(CASE, CASE == T);
  }
  return 0;
}

Fenwick Tree

#include <bits/stdc++.h>
// #include<bits/extc++.h>
// #define int long long//__int128
#define mmst0(x) memset(x, 0, sizeof(x))
#define mmst3f(x) memset(x, 0x3f, sizeof(x))
#define si(x) scanf("%d", &x)  // scanf("%lld",&x) // When define int ll
#define pb(x) emplace_back(x)
#define mkp(x, y) make_pair(x, y)
#define fi first
#define se second
#define YESS printf("Yes\n")
#define NOO printf("No\n")
#define fori(i, a, b, c) for (int(i) = (a); (i) <= (b); (i) += c)
#define ford(i, a, b, c) for (int(i) = (a); (i) >= (b); (i) -= c)
using namespace std;
// using namespace __gnu_pbds; // If using pbds don't using std!
using ll = long long;
// typedef long double rld; // use double pls!
using ull = unsigned long long;

const double eps = 1e-6;
const int INF = 0x3f3f3f3f;  // 0x3f3f3f3f3f3f3f3f; // LLINF
const int MAXN = (int)1e6 + 3;

inline char nc() {
  static char buf[100000], *p1 = buf, *p2 = buf;
  return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2)
             ? EOF
             : *p1++;
}
inline int read() {
  int s = 0, w = 1;
  char ch = nc();
  while (!isdigit(ch)) {
    if (ch == '-') w = -1;
    ch = nc();
  }
  while (isdigit(ch)) {
    s = (s << 3) + (s << 1) + (ch ^ 48);
    ch = nc();
  }
  return s * w;
}
// inline int read() {int x;si(x);return x;} // FAKE QUICK READ,JUST FOR DEBUG
//  inline void read(int &x){char ch=nc();x=0;while (!(ch>='0'&&ch<='9'))
//  ch=nc();while (ch>='0'&&ch<='9') x=(x<<3)+(x<<1)+ch-48,ch=nc();} //
//  根据参数个数自动选择 void prt(int
//  x){if(x<0){putchar('-');x=-x;}if(x>9)prt(x/10);putchar((char)(x%10+'0'));}
inline int lowbit(int x) { return x & (-x); }
int tree[MAXN];
inline void update(int i, int x) {
  for (int pos = i; pos < MAXN; pos += lowbit(pos)) tree[pos] += x;
}
inline int query(int n) {
  int ans = 0;
  for (int pos = n; pos; pos -= lowbit(pos)) ans += tree[pos];
  return ans;
}
inline int query(int l, int r) { return query(r) - query(l - 1); }
int n, m, op, a, b;

inline void work(signed CASE = 1, bool FINAL_CASE = false) {
  n = 2;
  for (int i = 1; i <= n; i++) update(i, read());
  cout << query(1, 2);
}
signed main() {
  // ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
  // //freopen(".in", "r", stdin);//freopen(".out", "w", stdout);
  signed T = 1;  //(signed)read();//scanf("%d",&T);// cin >> T;
  for (signed CASE = 1; CASE <= T; CASE++) {  //
    // printf("Case #%d: ",CASE); //printf("Case %d: ",CASE); //printf("Case
    // #%d: \n",CASE); //printf("Case %d: \n",CASE); while(cin>>n) work(n);
    work(CASE, CASE == T);
  }
  return 0;
}

#include<bits/stdc++.h>
//#include<bits/extc++.h>
//#define int long long//__int128
#define mmst0(x) memset(x,0,sizeof(x))
#define mmst3f(x) memset(x,0x3f3f3f3f,sizeof(x))
#define si(x) scanf("%d",&x) //scanf("%lld",&x) //When define int ll
#define pb(x) emplace_back(x)
#define mkp(x, y) make_pair(x, y)
#define fi first
#define se second
#define YESS printf("YES\n")
#define NOO printf("NO\n")
//#define len (r-1+1)
using namespace std;
//using namespace __gnu_pbds; //If using pbds don't using std!
typedef long long ll;
//typedef long double rld; //use double pls!
typedef unsigned long long ull;
typedef pair<int, int> PII;

const double eps = 1e-6;
const int INF=0x3f3f3f3f;//0x3f3f3f3f3f3f3f3f;//LLINF
const int MAXN=(int)75+3;
const int N=505;
const int M=55;
const int maxn=510;
const int mod=1e9;
const int inf=0x7f7f7f7f;

inline char nc() {
    static char buf[100000],*p1=buf,*p2=buf;
    return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline int read() {
    int s=0,w=1;
    char ch=nc();
    while(!isdigit(ch)) {
        if(ch=='-')w=-1;
        ch=nc();
    }
    while(isdigit(ch)) {
        s=(s<<3)+(s<<1)+(ch^48);
        ch=nc();
    }
    return s*w;
}
//inline int read() {
//  int x;    // FAKE QUICK READ,JUST FOR DEBUG
//  si(x);
//  return x;
//}
//inline void read(int &x){char ch=nc();x=0;while (!(ch>='0'&&ch<='9')) ch=nc();while (ch>='0'&&ch<='9') x=(x<<3)+(x<<1)+ch-48,ch=nc();}//根据参数个数自动选择
//void prt(int x){if(x<0){putchar('-');x=-x;}if(x>9)prt(x/10);putchar((char)(x%10+'0'));}

int a1[maxn],b1[maxn],c[maxn];

inline void work(int CASE=1,bool FINAL_CASE=false) {
	string a,b;
	cin>>a>>b;
	int len=max(a.length(),b.length());
	for(int i=a.length()-1,j=1;i>=0;i--,j++)a1[j]=a[i]-'0';
	for(int i=b.length()-1,j=1;i>=0;i--,j++)b1[j]=b[i]-'0';
	for(int i=1;i<=len;i++)
	{
		c[i]+=a1[i]+b1[i];
		c[i+1]=c[i]/10;
		c[i]%=10;
	}
	if(c[len+1])
		len++;
	for(int i=len;i>=1;i--)
		cout<<c[i];
	
    return ;
}

signed main() {
    //ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); //freopen(".in", "r", stdin);//freopen(".out", "w", stdout);
    //signed T=(signed)read();//scanf("%d",&T);//cin>>T;
    int T=1;
    for(int CASE=1; CASE<=T; CASE++) {
        //printf("Case #%d: ",Case);
        //while(cin>>n) work(n);
        work(CASE,CASE==T);
    }
    return 0;
}

A+B problems

a = int(input())
b = int(input())
print(a+b)