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

ll extGcd(ll a,ll b,ll& p,ll &q){
    if(b==0) {p=1; q=0; return a;}
    ll d = extGcd(b,a%b,q,p);
    q -= a/b * p;
    return d;
}
// return minimum x s.t. x>=0 and x=b0 (mod m0) and x=b1 (mod m1)
// if such x don't exist, return (0,-1)
// O(log(m0)+log(m1))
// Note that the risk of overflow
pair<ll,ll> CRT(ll b0,ll m0,ll b1,ll m1){
    ll p,q;
    ll d = extGcd(m0,m1,p,q);
    if((b1-b0)%d!=0) return make_pair(ll(0),ll(-1));
    ll m = m0/d * m1;
    ll tmp = (b1-b0)/d * p % (m1/d);
    ll r = (b0 + m0 * tmp) % m;
    return make_pair(r,m);
}
int main(){
    vector<ll> x(3),y(3);
    for(int i=0;i<3;i++) cin>>x[i]>>y[i];
    auto ret = CRT(x[0],y[0],x[1],y[1]);
    if(ret.second==-1){
        cout<<-1<<endl;
        return 0;
    }    
    ret = CRT(ret.first,ret.second,x[2],y[2]);
    cout<<ret.first<<endl;
    return 0;
}