#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>

using namespace std;

int main() {
  int n;
  double a, b;
  cin >> n >> a >> b;
  double r = (0.5 / a - 0.5 / b) * 0.5;
  double x = (0.5 / a + 0.5 / b) * 0.5;
  double y = (n - 1) * r;
  double d1 = hypot(x, y) - r;
  double d2 = hypot(x, y) + r;
  double ans = 1 / d1 - 1 / d2;
  printf("%.20f\n", ans / 2);
}