#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,m=3,i,j;
	double max=0.0,mj=0.0;
	cin>>n;
	int a[n][m];
	for(i=0;i<n;i++){
		for(j=0;j<m;j++){
			cin>>a[i][j];
			}
	 }
	 for(i=0;i<n;i++){
	 	mj=0.0;
	 	mj=(a[i][m-3]+a[i][m-2])*a[i][m-1]/2.0;
	 	if(max<mj){
	 		max=mj;
	 	}
	 }
	 printf("%.1f",max);
}

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