#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
int a[10000][10000];
int sum[1000];
int k;
int main()
{
	int n, i,j,m;
	cin >> n>>m;
	for (i = 0; i < n; i++) {
		for (j = 0; j < m; j++) {
			cin >> a[i][j];
		}
	}
	for (i = 0; i < n; i++) {
		int t = 0;
		for (j = 0; j < m; j++) {
			if (a[j] > a[j + 1]) {
				t = a[i][j];
				a[i][j] = a[i][j + 1];
				a[i][j + 1] = t;
			}
		}
	}
	for (i = 0; i < n; i++) {
		for (j = 1; j < m - 1; j++) {
			sum[k] += a[i][j];
		}
		k++;
	}
	int length = sizeof(sum) / sizeof(int);
	sort(sum, sum + length + 1);
	printf("%.2f", (float)sum[length - 1]);
	return 0;
}