#include <bits/stdc++.h>
using namespace std;
const int N=12;
int a[12][12]= {0};
int main() {
	int n,m;
	cin>>n>>m;
	for(int i=1; i<=n; i++) {
		for(int j=1; j<=m; j++) {
			cin>>a[i][j];
			a[i][j]+=a[i-1][j]+a[i][j-1]-a[i-1][j-1];
		}
	}
	int  ans=0;
	for(int x1=1; x1<=n; x1++) {
		for(int y1=1; y1<=m; y1++) {
			for(int x2=x1; x2<=n; x2++) {
				for(int y2=y1; y2<=m; y2++) {
					if((y2-y1+1)*(x2-x1+1)%2==1) continue;
					int now=a[x2][y2]-a[x1-1][y2]-a[x2][y1-1]+a[x1-1][y1-1];
					if((y2-y1+1)*(x2-x1+1)/2==now) {
						ans=max(ans,2*now);
					}
				}
			}
		}
	}
	cout<<ans;
	return 0;
}