#include<bits/stdc++.h>
using namespace std;
int main(){
	double max=0;
	int n;
	cin>>n;
	int a[100][100];
	int i,j;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
		}
	}
	double mianji;
	for(i=0;i<n;i++){
		mianji=(a[i][0]+a[i][1])*1.0*a[i][2]/2;
		if(mianji>max){
			max=mianji;
		}
	}
	cout<<fixed<<setprecision(1)<<max;
	return 0;
}
/**************************************************************
	Problem: 1330
	User: admin
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/