#include <bits/stdc++.h>
//define
#define yes (cout<<"Yes"<<endl)
#define no (cout<<"No"<<endl)
#define ll long long
#define str string
using namespace std;
int inf=2000000000;


int main(){
int A,B,a,b;cin>>A>>B>>a>>b;
int ans=a;
while(1){
    if(ans%A==a&&ans%B==b){
        cout<<ans<<endl;
        return 0;
    }
    else{
        ans+=A;
    }
    //cout<<ans<<endl;
}
}