#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef long long ll_t;

ll_t exgcd(ll_t a, ll_t b, ll_t &x, ll_t &y)
{
  if(b == 0) {
    x = 1; y = 0;
    return a;
  } else {
    ll_t d = exgcd(b, a % b, y, x);
    y -= a / b * x;
    return d;
  }
}

ll_t modmul(ll_t x , ll_t y , ll_t mod){
    if(x >= mod) x %= mod;
    if(y >= mod) y %= mod;
    if(x == 0 || y == 0) return 0;

    if(x < 1000000000000000000LL / y){
        return x * y % mod;
    }

    ll_t t = x;
    ll_t res = 0;
    for(; y ; y >>= 1){
        if(y & 1) {
            res = res + t;
            if(res >= mod) res -= mod;
        }
        t <<= 1;
        if(t >= mod) t -= mod;
    }
    return res;
}


bool modular(ll_t a1, ll_t m1 , ll_t a2 , ll_t m2 ,
             ll_t &val , ll_t& mod){
    a1 %= m1 ; a2 %= m2;
    if(a1>a2) return modular(a2,m2,a1,m1,val,mod);
    ll_t A,B,g = exgcd(m1,m2,A,B);
    if(a1%g != a2%g) return false;
    ll_t M = a1%g ;
    a1/=g ; m1/=g; a2/=g ; m2/=g;
    ll_t k = modmul(A+m2,a2-a1,m2);
    mod = m1*m2*g;
    val = (a1+modmul(modmul(k,m1,mod),g,mod)+M) % mod;
    return true;
}

int main()
{
    int n;
    //cin>>n;
    n = 3;
    ll_t a=0,b=1;
    FOR(i,n){
        unsigned long long x,y;
        cin>>x>>y;
        if(!modular(a,b,x,y,a,b)){
            puts("-1");
            return 0;
        }
    }
    if(a == 0) a = b;
    cout<<a<<endl;
    return 0;
}