#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
int l3, l4, l5;
double calc3(double r) {
  double x = r / 2;
  double y = r / 6 * sqrt(3);
  double z = sqrt(r * r - x * x - y * y);
  double ret = z * r * r / 12 * sqrt(3);
  return ret;
}
double calc4(double r) {
  double x = r / 2;
  double y = r / 2;
  double z = sqrt(r * r - x * x - y * y);
  double ret = z * r * r / 3;
  return ret;
}
double calc5(double r) {
  double x = r / 2;
  double y = r / 2 * (sqrt(5) + 1) / sqrt(10 - 2 * sqrt(5));
  double z = sqrt(r * r - x * x - y * y);
  double ret = z * r * r * 5 / 4 / sqrt(5 - sqrt(20)) / 3;
  return ret;
}
void run() {
  scanf("%d%d%d", &l3, &l4, &l5);
  printf("%.12lf\n", calc3(l3) + calc4(l4) + calc5(l5));
}
int main() {
  run();
  return 0;
}
