a=int(input())
b=1
c=1
for j in range(2,a+1):
    for i in range(2,j+1):
        c*=i
    b+=c
    c=1
print(b)

Python

Python

人生苦短，我用Py

n = int(input())

ans = 0

while n > 0:
    x = n
    res = 1
    while x > 0:
        res *= x
        x -= 1
    ans += res
    n -= 1

print(ans)

C++

依旧朴实无华

#include<bits/stdc++.h>
#include<string>
using namespace std;

int a[10000];
int b[10000];
int c[10000];
int ans[10000];

int main()
{

    int o;
    cin >>o;
    int la,lb,lc;
    ans[1]=1;
    if(o==1){cout<<"1";}
    else{
        for(int po=2; po<=o; po++){
            for(int i=2; i<=po; i++){
                if(i==2){
                    la=1;
                    a[1]=1;
                }
                else{
                    la=lc;
                }
                lb=0;
                int k=i;
                for(int j=1; j>0; j++){
                    lb++;
                    b[j]=k%10;
                    k=k/10;
                    if(k<10 && k!=0){
                        b[j+1]=k;
                        lb++;
                        break;
                    }
                    if(k==0){break;}
                }
                lc=lb+la;
                for(int j=1; j<=la; j++){
                    for(int t=1; t<=lb; t++){
                        c[t+j-1]=a[j]*b[t]+c[t+j-1];
                        c[t+j]=c[t+j]+c[t+j-1]/10;
                        c[t+j-1]=c[t+j-1]%10;
                    }
                }
                if(c[lc]==0){lc--;}
                for(int j=1; j<=lc; j++){
                    a[j]=c[j];
                    c[j]=0;
                }
            }
            for(int i=1; i<=lc; i++){
                ans[i]=ans[i]+a[i];
                ans[i+1]=ans[i+1]+ans[i]/10;
                ans[i]=ans[i]%10;
                a[i]=0;//归零
                b[i]=0;
                c[i]=0;
            }
        }
        if(ans[lc+1]!=0){lc++;}
        for(int i=lc; i>=1; i--){
            cout<<ans[i];
        }
    }

	return 0;
}