#include<stdio.h>

int main()
{
	int a[100][20],i,j;
	int n,m;
	int max,min;
	double score,maxscore,sum;
	scanf("%d %d",&n,&m);
	for(i=0;i<n;i++)
	{
		for(j=0;j<m;j++)
		{
			scanf("%d",a[i][j]);
		}
	}
	for(i=0;i<n;i++)
	{
		sum=0,max=0,min=0;
		maxscore=0;
		for(j=0;j<m;j++)
		{
			if(a[i][j]>max)
			max=a[i][j];
			if(a[i][j]<min)
			min=a[i][j];
			sum+=a[i][j];
		}
		score=(sum-max-min)/(m-2);
		if(score>maxscore)
		maxscore=score;
	}
	printf("%.2lf",maxscore);
	return 0;
}