#ifdef LOCAL111
#else
	#define NDEBUG
#endif
#include <bits/stdc++.h>
const int INF = 1e9;
using namespace std;
template<typename T, typename U> ostream& operator<< (ostream& os, const pair<T,U>& p) { cout << '(' << p.first << ' ' << p.second << ')'; return os; }

#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define RBP(i,a) for(auto& i : a)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
	template<typename T> void dpite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
#else
	#define DEBUG(x) true
	template<typename T> void dpite(T a, T b){ return; }
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
#define rangej(a,b,c) ((a) <= (c) and (c) < (b))
#define rrangej(b,c) rangej(0,b,c)
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<LL,LL> P;
typedef pair<LL,LL> LP;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);	
}

template <typename T>
long long gcd(T x, T y){
	return y==0 ? x : gcd(y, x%y);
}

//res.first*a+res.second*b == 1 となるresを返す (a,bは互いに素)
pair<long long, long long> extgcd(long long a,long long b)
{
	if(b==1){
		return pair<long long, long long>(0,1);
	}
	pair<long long, long long> t=extgcd(b,a%b);
	return pair<long long, long long>(t.second,t.first-a/b*t.second);
}

P solve(LL x0, LL y0, LL x1, LL y1){
	LL c = x0-x1;
	LL a = y0;
	LL b = -y1;
	if(c < 0){
		a = -a;
		b = -b;
	}
	int sm0 = 1;
	int sm1 = 1;
	if(a < 0){
		sm0 = -1;
	}
	if(b < 0){
		sm1 = -1;
	}
	DEBUG(a); DEBUG(b); DEBUG(c);
	LL g = gcd(sm0*a,sm1*b);
	if(c != 0){
		if(c%g != 0){
			return {-1,-1};
		}
		auto ps = extgcd(sm0*a/g,sm1*b/g);
		ps.F *= sm0*c/g;
		ps.S *= sm1*c/g;
		DEBUG(ps.F);
		DEBUG(ps.S);
		LL ho = sm1*b/g;
		LL ge = ps.F;
		return {ho*y0,x0+y0*ge};
	}else{
		return {y0*sm1*b/g,x0};
	}
}

int main()
{
	ios_init();
	int x[3], y[3];
	while(cin >> x[0] >> y[0]) {
		REP(i,2) cin >> x[i+1] >> y[i+1];
		auto s1 = solve(x[0],y[0],x[1],y[1]);
		// cout << s1.F << ' ' << s1.S << endl;
		if(s1.F == -1){
			cout << -1 << endl;
			continue;
		}
		auto s2 = solve(s1.S,s1.F,x[2],y[2]);
		if(s2.F == -1){
			cout << -1 << endl;
			continue;
		}
		// cout << s2.F << ' ' << s2.S << endl;
		cout << (s2.S%s2.F+s2.F)%s2.F << endl;
		// cout << endl << endl << endl;
	}
	return 0;
}