#include <stdio.h>
#include <string.h>
#include <math.h>

double mark(int a[100][100], int n, int m) {
	int min, max, sum = 0;
	double end, tmp = 0;
	for (int i = 0; i < n; i++) {
		min = 11;
		max = -1;
		sum = 0;
		for (int j = 0; j < m; j++) {
			sum = sum + a[i][j];
			if (a[i][j] < min)
				min = a[i][j];
			else if (a[i][j] > max)
				max = a[i][j];
		}
		if (m > 2) {
			sum = sum - min - max;
			end = 1.0 * sum / (m - 2);
		} else
			end = 1.0 * sum / m ;

		if (tmp < end)
			tmp = end;
	}
	return tmp;
}

int main() {
	double mark(int a[100][100], int n, int m);
	int n, m;
	int a[100][100] = {0};
	scanf("%d %d", &n, &m);
	double max = 0;
	for (int i = 0; i < n; i++) {

		for (int j = 0; j < m; j++)
			scanf("%d", &a[i][j]);
	}
	max = mark(a, n, m);
	printf("%.2f", max);
	return 0;
}