#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,a[100][3]={0},i,j;
	float z=0,s=0;
	cin>>n;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
			
		}	
	}
	for(i=0;i<n;i++){
		s=(a[i][0]+a[i][1])*a[i][2]/2.0;
		if(s>z){
			z=s;
		}
	}printf("%.1f",z);
}
/**************************************************************
	Problem: 1330
	User: jiangyuanfeng
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2076 kb
****************************************************************/