#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/extc++.h>
using namespace std;
using ld = long double; 
const vector<int> dx = {0, 0, 1, -1};
const vector<int> dy = {1, -1, 0, 0};
#define vec vector
#define int long long
#define double long double
//cout<<setprecision(10)<<fixed<<..
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repp(i, x, n) for (int i = x; i < (int)(n); i++)
#define pii pair<int,int>
#define pq priority_queue
#define all(V) begin(V),end(V)
#define printpair(p) cout<<p.first<<" "<<p.second<<"\n"
#define tple tuple<int,int,int>
template<class T, class U> inline bool chmax(T &a, const U &b) { if (a < b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmin(T &a, const U &b) { if (a > b) { a = b; return true; } return false; }
#define mend(a,b) G[a].push_back(b)

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

    
    int A,B,a,b;cin>>A>>B>>a>>b;
    int ans=1e18;
    for(int i=0;i<=10000000;i++){
        if(i%A==a&&i%B==b){
            chmin(ans,i);
        }
    }
    cout<<ans<<"\n";

}