#include <bits/stdc++.h>
using namespace std;
int w, h, a;
int gcd(int a, int b) { return !b ? a : gcd(b, a % b); }
int main() {
  cin >> a >> h >> w;
  int Gcd = gcd(a + h, a + w);
  if (h < a || w < a || Gcd < a) {
    cout << "-1";
    return 0;
  }
  printf("%.10lf", (double)Gcd / (Gcd / a) - a);
  return 0;
}
