Pat class A - A + B format

A + B Format

Calculation a+b And output the sum in standard format ---- in other words , Add a comma every three digits from the lowest order （ Thousand separator ）, If the result is less than four digits, there is no need to add .

Input format

All in one line , Contains two integers a and b.

Output format

All in one line , Output in standard format a+b And .

Data range

−106≤a,b≤106−106≤a,b≤106

sample input ：

-1000000 9

sample output ：

-999,991

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    int c = a + b;
    string num = to_string(c);
    string res;
    
    for(int i = num.size() - 1, j = 0; i >= 0; i --)
    {
        res = num[i] + res;
        j ++;
        if(j % 3 == 0 && i && num[i - 1] != '-') res = ',' + res;
    }
    
    cout << res << endl;
    
    return 0;
}