#include<iostream.h>
#include<math.h>
int main()
{
    int a1,b1,a2,b2;
    cin>>a1>>b1>>a2>>b2;
if(a2<=a1)
cout<<a1;
else
if(abs(a1-a2)<b1)
cout<<a2;
else{
    while(a1<a2)
    {
        a1+=b1;
    a2-=b2;
}
if(a1>a2)
cout<<a1;
else
cout<<a2;
}
return 0;
}
Where I'm wrong?Please help!Thank in advance!!!