#include <bits/stdc++.h>
using namespace std;
double Pi = acos(-1.0);
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  double ans = 0;
  ans += sqrt(2.0) * a * a * a / 12 + sqrt(2.0) * b * b * b / 6;
  double l = 0;
  l = 0.5 * c / sin(Pi / 180 * 36);
  double h = sqrt(c * c - l * l);
  double s = l * cos(Pi / 180 * 36) * c / 2 * 5;
  ans += h * s / 3;
  printf("%.12f\n", ans);
}
