#include <bits/stdc++.h>
using namespace std;

int main() {
    int A,B,a,b;
    cin >> A >> B >> a >> b;
    int aa=0,bb=0,i=0,j=0,check=0;
    while(true){
        aa=A*i+a;
        while(true){
            bb=B*j+b;
            if(aa==bb){
                cout << aa << endl;
                return 0;
            }
            else if(aa<bb){
                break;
            }
            else{
                j++;
            }
        }
        i++;
    }
}