#include <bits/stdc++.h>
using namespace std;
 
int main() {
  double a,b,c;
  cin >> a >> b >> c;
  double s;
  s=(a+b+c)/2;
  double tri;
  tri=sqrt(s*(s-a)*(s-b)*(s-c));
  double count=0;
  for(int i=0; i<200;i++){
    for(int j=0; j<200;j++){
      for(int k=0; k<200;k++){
        count += tri*(1-(1-i/200)*(j/200)-(1-j/200)*(k/200)-(1-k/200)*(i/200));
      }
    }
  }
  cout << count/32000000 << endl;
}