#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;
//using mint = modint1000000007;
//using mint = modint998244353;



int main(){
  vector<ll> x(3), y(3);
  rep(i,3){
    cin >> x[i] >> y[i];
  }

  auto res = crt(x, y);

  if(res.second == 0) cout << -1 << endl;
  else cout << res.first << endl;
  
  return 0;
}