90!!!!!!!!

#include<bits/stdc++.h>
using namespace std;
int a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z;
int main(){
    
    cin>>a>>b>>c>>d;
    if(a == 0){
        if(c != 0){
            cout<<-1;
        }
        else{
            cout<<b / d;
        }
    }
    else if(b == 0){
        if(d != 0){
            cout<<-1;
        }
        else{
            cout<<a / c;
        }
    }
    else if(a / c == b / d){
        cout<<a / c;
    }
    else{
        cout<<-1;
    }
    
    return 0;
}