#include <bits/stdc++.h>
using namespace std;
int main() {
  double l1, l2, l3, v1, v2, v3, ans, h, s;
  cin >> l1 >> l2 >> l3;
  v1 = sqrt(2.0) / 12. * l1 * l1 * l1;
  v2 = sqrt(2.0) / 6. * l2 * l2 * l2;
  h = sqrt((3. - sqrt(5.)) / (5. - sqrt(5.)));
  s = sqrt(5.) * sqrt(5. + 2. * sqrt(5.)) / 4.;
  v3 = 1. / 3. * s * h * l3 * l3 * l3;
  ans = v1 + v2 + v3;
  printf("%.10f", ans);
  return 0;
}
