#include<bits/stdc++.h>
using namespace std;
int n,a[250][4],q,w,e;
float c[250],b=INT_MIN;
int main()
{
  cin>>n;
  for(int i=1;i<=n;i++){
    for(int j=1;j<=n;j++){
    cin>>a[i][j];
  }
  }
  for(int i=1;i<=n;i++){
    for(int j=1;j<=1;j++){
    c[i]=(a[i][j]+a[i][j+1])*a[i][j+2]*1.0/2;
    if(c[i]>=b) {
    b=c[i];
    q=a[i][j];
    w=a[i][j+1];
    e=a[i][j+2];
    }
   }
}
   printf("%.1f",(q+w)*e*1.0/2);
    return 0;
}
/**************************************************************
	Problem: 1330
	User: wangyousi
	Language: C++
	Result: Wrong Answer
****************************************************************/