#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
//using mint = modint998244353;
//using mint = modint1000000007;
typedef long long ll;
typedef unsigned long long ull;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const int MAX = 1e9;
const int MIN = -1*1e9;
const ll MAXLL = 1e18;
const ll MINLL = -1*1e18;
//const ll MOD = 998244353;
//const ll MOD = 1000000007;

int main()
{
    int A,B,C,D; cin >> A >> B >> C >> D;
    int Ans = 0;
    while(true)
    {
        if(Ans%A==C&&Ans%B==D)
        {
            cout << Ans << endl;
            return 0;
        }
        Ans++;
    }
    return 0;
}