1001. A+B Format (20)

#include <cstdio>
#include <iostream>
#include <cmath>
using namespace std;
int main(){
int a, b,str[100],k = 0;
cin >> a >> b;
int sum = a + b;
if (sum == 0){
cout << 0 << endl;
return 0;
}
if (sum < 0) {
sum = -sum;
cout << "-";
}
if (sum == 0){
cout << 0 << endl;
}
else {
while (sum) {
int s1 = sum % 10;
sum = sum / 10;
str[k++] = s1;
}
for (int i = k-1; i >= 0; i--) {
cout << str[i];
if ((i) % 3 == 0 && i != 0) cout << ",";
}
cout << endl;
}
return 0;
}