#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i,a[100][100]={0};
	float max=0.0,m;
	cin>>n;
	for(i=0;i<n;i++){
		cin>>a[i][0]>>a[i][1]>>a[i][2];
	}
	for(i=0;i<n;i++){
		m=(a[i][0]+a[i][1])*a[i][2]/2.0;
		if(m>max){
			max=m;
		}
	}
	printf("%.1f",max); 
} 
/**************************************************************
	Problem: 1330
	User: linyuhang
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2076 kb
****************************************************************/