#include <iostream>
#include <cmath>
#include <iomanip>

using namespace std;

int main() {
    double L, n, C;
    cin >> L >> n >> C;
    
    // Calculate the new length after expansion
    double L_prime = (1 + n * C) * L;
    
    // Calculate the radius of the circle
    double R = (L_prime * L_prime) / (8 * (L_prime - L));
    
    // Calculate the height (offset) from the center of the chord to the arc
    double offset = R - sqrt(R * R - (L / 2) * (L / 2));
    
    // Output the result with precision up to 3 decimal places
    cout << fixed << setprecision(3) << offset << endl;
    
    return 0;
}


死