#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100005;
const int mod = 1e9 + 7;
struct sort_pred {
  bool operator()(const long long &left, const long long &right) {
    return left > right;
  }
};
long long exp(long long a, long long b) {
  long long ans = 1;
  while (b != 0) {
    if (b % 2) ans = ans * a;
    a = a * a;
    b /= 2;
  }
  return ans;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double a, b, c;
  cin >> a >> b >> c;
  double vol = 0;
  vol += a * a * a / (6 * sqrt(2));
  vol += b * b * b * sqrt(2) / 6.0;
  vol += c * c * c * (5 + sqrt(5)) / 24.0;
  printf("%.15f\n", vol);
  return 0;
}
