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

#define all(a) a.begin(),a.end()
#define pb push_back
#define sz(a) ((int)a.size())

signed main(){
    ios_base::sync_with_stdio(0),cin.tie(0);
    int a,b,c; cin >> a >> b >> c;
    bool flag=0;
    if(c%a==0) cout << c/a << "\n",flag=1;
    if((b+c)%a==0) cout << (b+c)/a << "\n",flag=1;
    if(!flag) cout << "-1\n";
}