#include <bits/stdc++.h>
using namespace std;
int main() {
  long double sum = 0, x, y, z;
  cin >> x >> y >> z;
  z = (pow(z, 3) * (5 + sqrt(5))) / 24;
  y = (pow(y, 3) * sqrt(2)) / 6;
  x = (pow(x, 3) * sqrt(2)) / 12;
  sum = x + y + z;
  cout << setprecision(14) << sum << '\n';
  return 0;
}
