#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)
#define all(a) (a).begin(),(a).end()

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    
    int A, B, a, b;
    cin >> A >> B >> a >> b;
    
    int ans = a;
    while (true) {
        if (ans % B == b) {
            cout << ans << '\n';
            return 0;
        }
        ans += A;
    }
}