#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,i,j,b=0,g=0,q=0;
	float max=0,m[100];
	cin>>n;
	float a[n][3];
	for(i=0;i<n;i++){
		for(j=0;j<3;j++){
			cin>>a[i][j];
			if(j==0)
				b=a[i][j]; 
			if(j==1)
				g=a[i][j]; 
			if(j==2)
				q=a[i][j]; 		
		}
		m[i]=((b+g)*q*1.0)/2;
	}
	for(i=0;i<n;i++){
		if(m[i]>max)
			max=m[i];
	}
	printf("%.1f",max);
	return 0;
}

/**************************************************************
	Problem: 1330
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/