#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i=0; i<n; i++)
#define debug 0
#define YES cout << "Yes" << endl;
#define NO cout << "No" << endl;
using ll = long long;
using ld = long double;
const int mod = 998244353;
const int MOD = 1000000007;
const double pi = atan2(0, -1);
#include <time.h>
#include <chrono>

int main() {
	int A, B, a, b;
	cin >> A >> B >> a >> b;
	int x = a;
	while (true) {
		if (x % B == b) {
			cout << x << endl;
			return 0;
		}
		x += A;
	}
}