#include<iostream>
#include<iomanip>
#include<vector>
#include<cmath>
#include<cstdlib>
using namespace std;

template<typename T>
void sort(T a[], int n)
{
	int t;
	for (int i = 0; i < n-1; i++)
	{
		for (int j = i + 1; j < n; j++)
		{
			if (a[j]<a[i])
			{
				t = a[i];
				a[i] = a[j];
				a[j] = t;
			}
		}
	}
}

double fun(int a[], int n)
{
	double sum = 0;
	for (int i = 1; i < n-1; i++)
	{
		sum = sum + a[i];
	}
	return sum / (n - 2);
}

int main()
{
	int m, n;
	cin >> n >> m;
	int a[101][21];
	double b[21];
	for (int i = 0; i < n; i++)
	{
		for (int j = 0; j < m; j++)
		{
			cin >> a[i][j];
		}
	}

	for (int i = 0; i < n; i++)
	{
		sort(a[i], m);
	}

	for (int i = 0; i < n; i++)
	{
		b[i] = fun(a[i], m);
	}
	
	sort(b, n);
	cout << setiosflags(ios::fixed) << setprecision(2)<< b[n - 1];
	return 0;
}

c++卡在第二个测试点了