#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 250;
long long mod = 1e9 + 7;
const int N = 100005;
const double pi = acos(-1.0);
int main() {
  double a, b, c, ans = 0, h, d;
  cin >> a >> b >> c;
  d = a / sqrt(3);
  h = sqrt(a * a - d * d);
  ans += 1.0 / 3 * 0.5 * sqrt(3) / 2 * a * a * h;
  d = b / sqrt(2);
  h = sqrt(b * b - d * d);
  ans += 1.0 / 3 * b * b * h;
  d = c / 2 / sin(pi / 5);
  h = sqrt(c * c - d * d);
  ans += 1.0 / 3 * 5 * 0.5 * d * d * sin(2 * pi / 5) * h;
  printf("%.12f\n", ans);
  return 0;
}
