Here is my code:
#include <iostream>
using namespace std;
void main()
{    int a,da,b,db;
    cin >> a >> da >> b >> db;
    while(a<b)
    {    if(a>=b)
        {    cout << a;
            return;
        }
        a+=da;
        if(a>=b)
        {    cout << a;
            return;
        }
        b-=db;
    }
    cout <<  a;
}

What could be wrong in my code that it dont work in test #4?
Thanks a lot.