题解 | #添加逗号#

#include <iostream>
#include<string>
using namespace std;

int main() {


    string str;
    cin>>str;


    int count=0;
    for(int i=str.size()-1; i>0; i--){
        count++;
        if(count == 3){
            str.insert(i, ",");
            count=0;
        }

    }


    cout<<str<<endl;

return 0;
}
// 64 位输出请用 printf("%lld")