#include <bits/stdc++.h>
using namespace std;
int main() {
  double i3, i4, i5;
  cin >> i3 >> i4 >> i5;
  double I3, I4, I5;
  I3 = (sqrt(3) / 2.0 * i3 * i3 / 2.0 * sqrt(6) / 3.0 * i3) / 3.0;
  I4 = (i4 * i4 * sqrt(2) / 2.0 * i4) / 3.0;
  double pi = acos(-1), t = pi / 5.0, x = i5 / 2.0 / sin(t),
         y = sqrt(i5 * i5 - x * x);
  I5 = 0.5 * x * i5 * sin(54 / 180.0 * pi) * 5 * y / 3.0;
  printf("%.12lf\n", I3 + I4 + I5);
  return 0;
}
