#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int a, b, c;
  cin >> a >> b >> c;
  double v1 = sqrt(2) / 12.0 * a * a * a;
  double v2 = sqrt(2) / 6.0 * b * b * b;
  double h = sqrt(25.0 + 10.0 * sqrt(5)) / 10.0;
  double H = sqrt(1.0 - h * h - 0.50 * 0.50);
  double v3 = sqrt(25.0 + 10.0 * sqrt(5)) / 4.0 * H / 3.0 * c * c * c;
  printf("%.9f\n", v1 + v2 + v3);
  return 0;
}
