#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) for (int i = (a) - 1; i >= 0; i--)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 9;

ll x[3], y[3];

ll lcm(ll a, ll b) {
    return a / __gcd(a, b) * b;
}

void solve(ll x1, ll y1, ll x2, ll y2, ll &resX, ll &resY) {
    ll l = lcm(y1, y2);
    for (ll i = 0; x1 + y1 * i < l; i++) {
        ll z = x1 + y1 * i;
        if (z % y2 == x2) {
            resX = z;
            resY = l;
            return;
        }
    }

    resX = 0;
    resY = -1;
}

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

    solve(x[0], y[0], x[1], y[1], x[1], y[1]);

    if (y[1] == -1) {
        cout << -1 << endl;
        return 0;
    }
    
    solve(x[1], y[1], x[2], y[2], x[2], y[2]);

    if (y[2] == -1) {
        cout << -1 << endl;
        return 0;
    }

    if (x[2] == 0) x[2] += y[2];
    cout << x[2] << endl;
}