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

using int64 = long long;
using uint64 = unsigned long long;

int main()
{
    int n, a, b;
    cin >> n >> a >> b;

    double R = (1.0 / a - 1.0 / b) / 4.0,
           X = (1.0 / a + 1.0 / b) / 4.0,
           Y = (n - 1) * R;
    
    double ans = (1 / (sqrt(X * X + Y * Y) - R) - 1 / (sqrt(X * X + Y * Y) + R)) / 2.0;

    cout << fixed << setprecision(20) << ans << endl;

    return 0;
}