#include<bits/stdc++.h>
#include<atcoder/math>
using namespace std;
int main() {
	int N = 3;
	vector<long long> X(N), Y(N);
	for (int i = 0; i < N; i++) {
		cin >> X[i] >> Y[i];
	}
	pair<long long, long long> P = atcoder::crt(X, Y);
	long long ans = P.first;
	if (P.first == 0) ans = P.second;
	if (P == make_pair(0LL, 0LL)) {
		ans = -1;
	}
	cout << ans << endl;
}