1001. A+B Format

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

int main(void){
int a,b,cnt=0;
stack<char> sum1;
string s1,s2;
cin>>s1>>s2;
a=stoi(s1);
b=stoi(s2);
int sum=a+b;
if(sum<0){
cout<<'-';
sum=-sum;
}
string sum2=to_string(sum);
for(auto r_iter = sum2.crbegin();r_iter != sum2.crend();++r_iter){
if(cnt==3){
sum1.push(',');
cnt=0;
}
sum1.push(*r_iter);
cnt++;
}
while(!sum1.empty()){
cout<<sum1.top();
sum1.pop();
}

return 0;
}