#include <bits/stdc++.h>
signed main() {
  double l3, l4, l5;
  std::cin >> l3 >> l4 >> l5;
  double r3, r4, r5;
  double h3, h4, h5;
  double s3, s4, s5;
  r3 = sqrt(l3 * l3 - l3 * l3 / 4) * 2 / 3;
  h3 = sqrt(l3 * l3 - r3 * r3);
  s3 = l3 * sqrt(l3 * l3 - l3 * l3 / 4) / 2 * h3 / 3;
  r4 = sqrt(2 * l4 * l4) / 2;
  h4 = sqrt(l4 * l4 - r4 * r4);
  s4 = l4 * l4 * h4 / 3;
  r5 = sqrt(50 + 10 * sqrt(5)) * l5 / 10;
  h5 = sqrt(l5 * l5 - r5 * r5);
  s5 = sqrt(25 + 10 * sqrt(5)) * l5 * l5 / 4 * h5 / 3;
  printf("%.9lf", s3 + s4 + s5);
}
