#include<bits/stdc++.h>
using namespace std;
int  main(){
    int n,a,b,h;
	float s=0,mx=0;
	cin>>n;
	for(int i=1;i<=n;i++){
	    cin>>a>>b>>h;
	    s=(a+b)*h*1.0/2;
	    if(s>=mx)   mx=s; 
	}	
	cout<<mx<<endl;
	
	
	return 0;
}

/**************************************************************
	Problem: 1330
	User: chenyaohuo
	Language: C++
	Result: Wrong Answer
****************************************************************/