#include <bits/stdc++.h>
using namespace std;
int calc_gcd(int x, int y) {
  int r = x % y;
  while (r) x = y, y = r, r = x % y;
  return y;
}
int main() {
  int a, w, h, g;
  scanf("%d %d %d", &a, &h, &w);
  g = calc_gcd(a + h, a + w);
  if (h < a || w < a || g < a) {
    printf("-1");
    return 0;
  }
  printf("%.10lf", 1.0 * g / (g / a) - a);
  return 0;
}
