#include<cstdio>
#include<iostream>
using namespace std;
int main(){
	int m,n,a[101][21];
	double b[101];
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			cin>>a[i][j];
		}
	}
	double max=0,min=999,max1=0,sum=0;
	int idxmax,idxmin;
	for(int i=1;i<=n;i++){
		sum=0;
		for(int j=1;j<=m;j++){
			if(a[i][j]>max){
				idxmax=j;
				max=a[i][j];
			} 
			if(a[i][j]<min){
				idxmin=j;
				min=a[i][j];
			}
			sum+=a[i][j]; 
		}
		sum-=a[i][idxmax];
		sum-=a[i][idxmin];
		b[i]=sum/(m-2);
	}
	for(int i=1;i<=n;i++){
		if(b[i]>max1) max1=b[i];
	}
	printf("%.2lf",max1);
	return 0;
}