#include<bits/stdc++.h>
using namespace std;
int n,i,j;
float a[101][101],max_;
int main(){
	cin>>n;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
		}
	}
	for(i=0;i<n;i++){
		a[i][3]=(a[i][0]+a[i][1])*a[i][2]*1.0/2;
	}
	max_=a[0][3];
	for(i=1;i<n;i++){
		if(a[i][3]>max_) max_=a[i][3];
	}
	cout<<max_;
	return 0;
}
/**************************************************************
	Problem: 1330
	User: zhangziang
	Language: C++
	Result: Wrong Answer
****************************************************************/