#include <bits/stdc++.h>
using namespace std;
int a, h, w;
int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
int main() {
  cin >> a >> h >> w;
  int k = gcd(h + a, w + a);
  if (k < a || a > h || a > w)
    cout << -1;
  else
    cout << fixed << setprecision(10) << (double)k / (k / a) - a;
  return 0;
}
