#include <stdio.h>
double Average(int m,double a[])
{int i;
double sum=0,average,max,min;
for (i=0;i<m;i++)
	sum=sum+a[i];
max=a[0];
for (i=1;i<m;i++)
	if(max<a[i])
		max=a[i];
min=a[0];
for (i=1;i<m;i++)
	if(min>a[i])
		min=a[i];
sum=sum-max-min;
average=sum/(m-2);
return average;
}

int main ()
{int m,n,i,j;
double a[80][80]={0},max;
scanf ("%d%d",&n,&m);
for (i=0;i<n;i++)
	for (j=0;j<m;j++)
		scanf ("%lf",&a[i][j]);
max=Average(m,a[0]);
for (i=1;i<n;i++)
	if (max<Average(m,a[i]))
		max=Average(m,a[i]);
printf ("%.2f",max);

return 0;
}