#include <stdio.h>
int main ()
{
	int a[101][20];
	float best=0.0;
	int i,j;
	scanf("%d%d",&i,&j);
	for(int m=1;m<=i;m++)
	{
		int sum=0,max=0,min=10;
		for(int n=1;n<=j;n++)
		{
			scanf("%d",&a[m][n]);
			if(a[m][n]>max)
				max=a[m][n];
			if(a[m][n]<min)
				min=a[m][n];
			sum=sum+a[m][n];
		}
		sum=sum-max-min;
		(float) sum;
		float  average=sum/(j-2);
		if(average>best)
		best=average;
		
	}
	printf("%.2f",best);
	
	return 0;
	
}