#include<bits/stdc++.h>
using namespace std;
int main()
{
	int st,ju,maxn=0,ju1[1001],minn=101;
	double sum[1001],big;
	cin >> st >> ju;
	for(int i=0;i<st;i++)
	{
		for(int j=0;j<ju;j++)
		{
			cin >> ju1[j];
			sum[i]+=ju1[j];
			if(ju1[j]>maxn)maxn=ju1[j];
			if(ju1[j]<minn)minn=ju1[j]; 
	    }
		sum[i]=(sum[i]-maxn-minn)/(ju-2);
		if(sum[i]>sum[i-1])
		    big=sum[i];
		else
		    continue;
		maxn=0,minn=101;
	}
	printf("%.2lf",big);
	return 0;
}