#include<bits/stdc++.h> using namespace std; int main(){ double a,b,c; cin>>a>>b>>c; double p=(a+b+c)/2; cout<<"area="; cout<<sqrt((a+b+c/2)*(a+b+c/2-a)*(a+b+c/2-b)*(a+b+c/2-c))<<endl; return 0; }