#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<1000;i++){
    for(int j=0; j<1000;j++){
      for(int k=0; k<1000;k++){
        count += tri*(1-(1-i/1000)*(j/1000)-(1-j/1000)*(k/1000)-(1-k/1000)*(i/1000));
      }
    }
  }
  cout << count/4000000000 << endl;
}