#include <iostream>
#include <cmath>

using namespace std;

double r, p, q;
double a, b;

int main() {
    scanf("%lf%lf%lf", &r, &p, &q);
    if (fabs(r - q) > 1e-4) printf("0\n");
    else {
        double a = r * sqrt(2);
        double b = (r + p) * sqrt(2);
        printf("%.4lf\n", a * b);
    }
    return 0;
}