#include<bits/stdc++.h>
using namespace std;
int main(){
	int a[100][100]={0},n,i,j;
	float x;
	cin>>n;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
		}
	}
	x=(a[0][0]+a[0][1])*a[0][2]/2.0;
	for(i=1;i<n;i++){
		if(x<(a[i][0]+a[i][1])*a[i][2]/2.0) x=(a[i][0]+a[i][1])*a[i][2]/2.0;
	}
	printf("%.1f",x);
}
/**************************************************************
	Problem: 1330
	User: linzihang
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2076 kb
****************************************************************/