#include <iostream>
#include <iomanip>
using namespace std;
int main() {
    int n, m;
    cin >> n >> m;
    int bb = -1000;
    for(int i = 0; i < n; i++) {
        int b = -1000, s = 1000;
        double sum = 0;
        for(int j = 0; j < m; j++) {
            int t;
            cin >> t;
            if(t > b) {
                b = t;
            }
            if(t < s) {
                s = t;
            }
            sum += t;
        }
        sum = sum - b - s;
        sum = 1.0*sum/(m-2);
        if(sum > bb) {
            bb = sum;
        }
    }
    cout << fixed << setprecision(2) << 1.0*bb << endl;
    return 0;
}

在线等，急！