#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;


int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll a,b,c,d;
    cin>>a>>b>>c>>d;
    int x = 0;
    while(true){
        if(x%a==c&&x%b==d){
            cout<<x<<endl;
            return 0;
        }
        x++;
    }
}