#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <algorithm>
#include <cmath>
#include <cassert>
#include <iomanip>
using namespace std;
int n, a, b;
int main() {
	cin >> n >> a >> b;
	cout << fixed << setprecision(15) << 4 * a*b*(b - a) / (double)((((double)n*n - 2 * n)*(b - a)*(b - a)) + (a + b)*(a + b)) << endl;
	return 0;
}