import base64

print(base64.b64encode(input().encode('ascii')).decode('ascii'))

位运算。

#include<bits/stdc++.h>
using namespace std;
string s;
char to_char(int x)
{
	if (x<26)
		return x+65;
	if (x<52)
		return x+71;
	if (x<62)
		return x-4;
	if (x==62)
		return '+';
	if (x==63)
		return '/';
}
int main()
{
	getline(cin,s);
	for (int i=0;i<s.length();i+=3)
		printf("%c%c%c%c",to_char(s[i]>>2),to_char(((s[i]%4)<<4)+(s[i+1]>>4)),to_char(((s[i+1]%16)<<2)+(s[i+2]>>6)),to_char(s[i+2]%64));
	return 0;
}

s=input()
a=[0]*1000
b=[0]*4000
dic="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
for i in range(len(s)):
    a[i]=ord(s[i])
k=len(s)//3
for i in range(k):
    b[i*4+0]=a[i*3+0]//4
    b[i*4+1]=a[i*3+0]%4*16+a[i*3+1]//16
    b[i*4+2]=a[i*3+1]%16*4+a[i*3+2]//64
    b[i*4+3]=a[i*3+2]%64
for i in range(k*4):
    print(dic[b[i]],end="")

s=input()
a=[0]*1000
b=[0]*4000
dic="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
for i in range(len(s)):
    a[i]=ord(s[i])
k=len(s)//3
for i in range(k):
    b[i*4+0]=a[i*3+0]//4
    b[i*4+1]=a[i*3+0]%4*16+a[i*3+1]//16
    b[i*4+2]=a[i*3+1]%16*4+a[i*3+2]//64
    b[i*4+3]=a[i*3+2]%64
for i in range(k*4):
    print(dic[b[i]],end="")