#include <bits/stdc++.h>
using namespace std;

double solve(int n, double a, double b){
    double ka, kb, k3;
    ka = 1/a;
    kb = -1/b;
    if (n % 2){
        k3 = 1/(b - a);
        n = (n - 1) / 2;
    }else{
        k3 = (a + b) * (a + b) / (4 * a * b * (b - a));
        n = (n - 2) / 2;
    }
    double c1 = ka + kb;
    double c2 = ka * kb;
    while (n--){
        k3 = c1 + k3 + 2 * sqrt(abs(c2 + c1 * k3));
    }
    return 1/k3;
}

int main() {
    int n;
    double a, b;
    cin >> n >> a >> b;
    cout << fixed << setprecision(9) << solve(n, a, b) << endl;
    return 0;
}