#include<bits/stdc++.h>
using namespace std;
double maxd(double a, double b) {
	if (a > b) 
		return a;
	else 
		return b;
}
double mind(double a, double b) {
	if (a > b) 
		return b;
	else 
		return a;
}
int main() {
	double n,m;
	double tmp[101][101];
	double maxi,mini;
	double maxn=-1;
	double sum;
	cin>>n>>m;
	for(int i=0;i<n;i++){
		sum=0;
		maxi=0;
		mini=999;
		for(int j=0;j<m;j++){
			cin>>tmp[i][j];
			maxi=maxd(maxi,tmp[i][j]);
			mini=mind(mini,tmp[i][j]);
			sum+=tmp[i][j]; 
		}
		sum-=maxi+mini;
		sum/=m;
		maxn=maxd(maxn,sum);
	}
	cout<<fixed<<setprecision(2)<<maxn;
	return 0;
}
``