#include<bits/stdc++.h>
using namespace std;
int main()
{
	int v[105][3];
	int n,a,b,h;
	float max=0,max_2;
	cin>>n;
	for(int i=0;i<n;i++){
		for(int j=0;j<3;j++){
			cin>>v[i][j];
	 	
		}
		a=v[i][0];
		b=v[i][1];
		h=v[i][2];
		max_2=((a+b)*h)/2.0;
		if(max<max_2)max=max_2;
	}
	
	printf("%.1f",max);
	

	

	return 0;
}

/**************************************************************
	Problem: 1330
	User: hbq
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/