#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c;
  scanf("%d%d%d", &a, &b, &c);
  double pi = acos(-1);
  double s1 = sqrt(2) * a * a * a / 12;
  double s2 = sqrt(2) * b * b * b / 6;
  double l = c / sin(pi / 5) / 2;
  double h = sqrt(c * c - l * l);
  double s = 5 * l * l * sin(2 * pi / 5) / 2;
  double s3 = h * s / 3;
  printf("%.12f\n", s1 + s2 + s3);
}
