#include <bits/stdc++.h>
using namespace std;

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define UB upper_bound
#define LB lower_bound
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

LL ex_gcd(LL a, LL b, LL & x, LL & y) {
	LL d = a;
	if(b != 0) {
		d = ex_gcd(b, a % b, y, x);
		y -= (a / b) * x;
	} else { x = 1; y = 0; }
	return d;
}
LL im(LL x, LL y) { return (x % y + y) % y; }
bool crt(LL & r1, LL & m1, LL r2, LL m2) {
	LL x1, x2, d;
	d = ex_gcd(m1, m2, x1, x2);
	if((r1 - r2) % d != 0) { return false; }
	r1 += (r2 - r1) / d * x1 * m1;
	m1 *= m2 / d;
	r1 = im(r1, m1);
	return true;
}

int main() { // サンプル通らない……
	LL r = 0, m = 1;
	inc(i, 3) {
		LL x, y;
		cin >> x >> y;
		if(! crt(r, m, x, y)) { r = -1; break; }
	}
	
	if(r == 0) { r = m; }
	cout << r << endl;
	
	return 0;
}