#include<bits/stdc++.h>
using namespace std;
struct ss{
	int a,b,h;
	float s;
}m[100];
int main()
{
	int i,n;
	float max=0;
	cin>>n;
	for(i=0;i<n;i++){
		cin>>m[i].a>>m[i].b>>m[i].h;
		m[i].s=(m[i].a+m[i].b)*m[i].h/2.0;
		if(m[i].s>max)
			max=m[i].s;	
	}
	printf("%.1f",max);
return 0;
}

/**************************************************************
	Problem: 1330
	User: fzy001
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2076 kb
****************************************************************/