#include <iostream>
using namespace std;
int main() {
int a,b,c,d;
cin>>a>>b>>c>>d;
int i=0;
while(true)
{
if( ((b+c*i)/a)-int(((b+c*i)/a))==0)
{
break;
}
else
{
i++;
}
}
cout<<(i*c)+d<<endl;
// your code goes here
return 0;
}
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