#include <iostream>
#include <cmath>
#include <cstdio>
#include <algorithm>
using namespace std;
int main()
{
  double p,q,r,ab,ac,pq,s;
  int max_value=100000;
  cin>>p>>q>>r;
  if(p!=r) { cout<<'0'<<endl; return 0; }
  ab=sqrt((p*p)+(p*p));
  pq=p+q;
  ac=sqrt((pq*pq)+(pq*pq));
  s=ac*ab;
  printf("%.4lf",s);
  cout<<endl;
  return 0;
}
