#include <bits/stdc++.h>
using namespace std;
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};
bool app[26];
int main() {
  string t;
  long long a, b, c;
  cin >> a >> b >> c;
  long long res = (b / a) + (c / a);
  long long rm1 = b % a;
  long long rm2 = c % a;
  if ((rm1 && c < a) || (rm2 && b < a) || (b < a && c < a))
    cout << -1;
  else
    cout << res;
  return 0;
}
