#include <bits/stdc++.h>
using namespace std;
long long int a, b, c;
long long int re, mx, tmp;
void _love() { cin >> a >> b >> c; }
void _nang_am() {
  re = b / a;
  mx = c / a;
  if (re + mx == 0 || (a * (re + mx)) < max(b, c)) {
    cout << -1 << "\n";
  } else {
    cout << re + mx << "\n";
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  _love();
  _nang_am();
  return 0;
}
