#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i,j;
	cin>>n;
	int a[n][3];
	float max=0.0,s;
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
		}
	}
	for(i=0;i<n;i++){
			s=1.0*(a[i][0]+a[i][1])*a[i][2]/2;
		if(s>max){
			max=s;	
		}
		s=0;
	}
	printf("%.1f",max);
	return 0;
}

/**************************************************************
	Problem: 1330
	User: zouliangyin
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/