#include <iostream>
using namespace std;
int main(){
    long long a,b,c;cin>>a>>b>>c;
    bool ok = false;
    for(long long i = 1; 1000000 >= i; i++){
        if(i*a-b == c || (i*a-b <= 0 &&i*a == c)){
            ok = true;
            cout << i << endl;
        }
    }
    if(!ok)cout << -1 << endl;
}