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

void solve() {
    int a, b, c;
    cin >> a >> b >> c;
    bool flag = true;

    if (c <= b && c % a == 0) {
        flag = false;
        cout << (c / a) << '\n';
    }

    if ((b + c) % a == 0) {
        flag = false;
        cout << ((b + c) / a) << '\n';
    }

    if (flag) {
        cout << -1 << '\n';
    }
}

int main() {
    int q = 1;
    // cin >> q;
    while (q--) {
        solve();
    }
}