#include<bits/stdc++.h>
using namespace std;
int main(){
  int n, m;
    cin >> n >> m;
    vector<vector<double>> scores(n, vector<double>(m));
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            cin >> scores[i][j];
        }
    }
    double max_score = 0.0;
    for (int i = 0; i < n; ++i) {
        sort(scores[i].begin(), scores[i].end());
        double sum = 0.0;
        for (int j = 1; j < m - 1; ++j) {
            sum += scores[i][j];
        }
        double avg = sum / (m - 2);
        if (avg > max_score) {
            max_score = avg;
        }
    }
    cout << fixed << setprecision(2) << max_score << endl;
    return 0;
}```