#include <bits/stdc++.h>
using namespace std;
double a[105];
int tempx, tempn, templ;
double minf = 100001;
double maxf = -1.0;
double maxn = -1.0;
int main()
{
    long long x, y;
    cin >> x >> y;
    double ans = 0.0;
    for(long long i = 0; i < x; i++)
    {
        for(long long 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(long long 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;
        }
        ceil(ans /= (y - 2)*1.0);
        if(ans > maxn)
        {
            maxn = int(ans);
        }
        for(long long l = 0; l < y; l++)
        {
            a[l] = 0;
        }
        ans = 0;
    }
    cout << fixed << setprecision(2);
    cout << maxn << endl;
    return 0;
}

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