#include<stdio.h>
long i,j,k,l,n,m,d[200][200],s[200][200],ss[200][200],max;
FILE *fin,*fout;
int main()
{
	fin=fopen("long.in","rb");
	fout=fopen("long.out","wb");
	fscanf(fin,"%ld%ld\n",&n,&m);
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=m;j++)
			fscanf(fin,"%ld",&d[i][j]);
		fscanf(fin,"\n");
	}
	for(i=1;i<=n;i++)
	{
		s[i][1]=d[i][1];
		for(j=2;j<=m;j++)
			
				s[i][j]=s[i][j-1]+d[i][j];
	}
	for(i=1;i<=j;i++)
		ss[1][i]=s[1][i];
	for(i=2;i<=n;i++)
		for(j=1;j<=m;j++)
		ss[i][j]=ss[i-1][j]+s[i][j];
	max=0;
	for(i=0;i<=m;i++)
		for(j=i;j<=m;j++)
			for(k=0;k<=n;k++)
			{
				for(l=k;l<=n;l++)
				{
					long y=0;
					y=ss[l][j]-ss[k][j]-ss[l][i]+ss[k][i];
					if(y>0)
					{
						long aa,bb;
						aa=l-k;
						bb=j-i;
						if(k!=0)aa++;
						if(i!=0)bb++;
						max=aa*bb;
					}
				}
			}
	fprintf(fout,"%ld",max);
	fclose(fin);
	fclose(fout);
	return 0;
}