#include <bits/stdc++.h>
const double e = acos(-1) / 180.0;
int main() {
  double a, b, c;
  while (~scanf("%lf %lf %lf", &a, &b, &c)) {
    double s = sqrt(2.0) / 12.0 * a * a * a + sqrt(2.0) / 6.0 * b * b * b +
               5.0 / 12.0 *
                   sqrt(1.0 - 1.0 / (cos(54 * e) * cos(54 * e)) / 4.0) *
                   tan(54 * e) * c * c * c;
    printf("%.12f", s);
  }
  return 0;
}
