#include <bits/stdc++.h>
using namespace std;
int main() {
    long long A, B, C;
    cin >> A >> B >> C;
    int cnt = 0;
    if (C % A == 0 && C <= B) cout << C / A << endl, ++cnt;
    if ((B + C) % A == 0) cout << (B + C) / A << endl, ++cnt;
    if (!cnt) cout << -1 << endl;
}