#include<iostream> 
#include<cstdio>
using namespace std;
int a[100005],sum,m,n,x,ans=0,maxx=0,minn=1e9;
int main()
{
	cin>>n>>m;
	for(int j=1;j<=n;++j){
	a[j]=0;
	for(int i=1;i<=m;++i){cin>>x;ans+=x;minn=min(minn,x);maxx=max(maxx,x);}
	a[j]=(ans-maxx-minn)/(m-2);
    sum=max(a[j],sum);	
	ans=0;
	minn=1e9;
	maxx=0;
	}
    printf("%.2f",&sum);
    return 0;
}