#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,h,n;
	float d=0,s=0;
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>a>>b>>h;
		s=(a+b)*h/2.0;
		if(s>d){
			d=s;
		}
	}
	printf("%.1f",d);
} 
/**************************************************************
	Problem: 1330
	User: cyp
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/