#include <bits/stdc++.h>
using namespace std;
int a[25];
int tempx, tempn, templ;
int minf = 11;
int maxf = -1;
double maxn = -1.0;
int main()
{
    int x, y;
    cin >> x >> y;
    double ans = 0.0;
    for(int i = 0; i < x; i++)
    {
        for(int j = 0; j < y; j++)
        {
            cin >> a[j];
            if(a[j] > maxf)
            {
                maxf = a[j];
                tempx = j;
            }
            if(a[j] < minf)
            {
                minf = a[j];
                tempn = j;
            }
        }
        for(int k = 0; k < y; k++)
        {
            if(k != tempx && k != tempn)
            {
                ans += a[k]*1.0;
            }
        }
        ans /= (y - 2)*1.0;
        if(ans > maxn)
        {
            maxn = ans;
        }
        for(int l = 0; l < y; l++)
        {
            a[l] = 0;
        }
    }
    cout << fixed << setprecision(2);
    cout << maxn << endl;
    return 0;
}