#include<bits/stdc++.h>
using namespace std;
int main()
{
	float max=0,t,n,m;
	int i,j;
	cin>>n;
	float g[100][3];
	for(i=0;i<n;i++){
		t=0;
		for(j=0;j<3;j++){
			cin>>g[i][j];
		} 
		t=(g[i][0]+g[i][1])*g[i][2]/2;
		if(t>=max){
			max=t;
		}
	}
	printf("%.1f",max); 
	return 0;
}

/**************************************************************
	Problem: 1330
	User: zzz
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/