# include <fstream>
# include <iostream>
# define DIM 1003
# define max(a,b) (a>b?a:b)
# define shi short int
using namespace std;
shi n, m, a[DIM][DIM], b[DIM][DIM], v[DIM];
int sol;

void read ()
{
	ifstream fin ("dreptpal.in");
	fin>>n>>m;
	for(shi i=1;i<=n;++i)
		for(shi j=1;j<=m;++j)
			fin>>a[i][j];
}

void solve ()
{
	shi s, d;
	sol=n;
	for(shi i=1;i<=n;++i)	
		for(shi j=1;j<=m;++j)
		{
			b[i][j]=1;
			s=j-1;d=j+1;
			while (s && d<=m && a[i][s]==a[i][d])
				--s, ++d, b[i][j]+=2;
			sol=max(sol,b[i][j]);
		}
	shi dr;
	for (shi j=1;j<=m;++j)
	{
		dr=1;
		v[dr]=1;
		for(int i=2;i<=n;++i)
		{
			while (b[v[dr]][j]>=b[i][j] && dr)--dr;
			if (!dr)sol=max(sol,(int)b[i][j]*i);
			else sol=max(sol,(int)b[i][j]*((int)i-v[dr]));
			v[++dr]=i;
		}
	}
}

int main ()
{
	read ();
	solve ();
	ofstream fout ("dreptpal.out");
	fout<<sol;
}