Collecting Inputs

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

int main() {
    string line;
    // Read input line by line
    while (getline(cin, line)) {
        istringstream iss(line);
        int a, b;
        if (iss >> a) {
            if (iss >> b) {
                // Case: two numbers on the line
                cout << (a + b) << endl;
            } else {
                // Case: only one number on the line, sum its digits
                int sum = 0;
                while (a != 0) {
                    sum += a % 10;
                    a /= 10;
                }
                cout << sum << endl;
            }
        }
    }
    return 0;
}