#include <iostream>
using namespace std;
 
int sum(int a, int b);
 
int main()
{
        int x, y;
        x =-5; y = 9;
        cout << sum(x, y) << endl;
}
 
int sum(int a, int b)
{
        if (a == 0)
                return b;
        else
        return sum(a - 1, b + 1);
}

Timeout