#include<iomanip>
#include<algorithm>
#include<iostream>
using namespace std;
int main()
{
	int m, n, i, j, a[100][100], b[100], sum = 0;
	double max = 0;
	cin >> m >> n;
	for (i = 0;i < m;i++)
	{
		int k = 0;
		for (j = 0;j < n;j++)
		{
			cin >> a[i][j];
			b[k] = a[i][j];
			k++;
		}
		sort(b, b + n);
		for (int k = 1;k < n - 1;k++)
			sum += b[k];
		double ave = sum / (n - 2);
			sum = 0;
		if (max < ave) max = ave;
	}
	cout <<fixed<<setprecision(2)<< max << endl;
	return 0;
}