#include<stdio.h>

#define minim(a,b) (a<b ? a : b)
#define maxim(a,b) (a>b ? a : b)

int n,m,a[1005][1005];
int d[1005][1005],sol;

int main ()
{
    int i,j,st,dr,c,vmin;
    freopen("dreptpal.in","r",stdin);
    freopen("dreptpal.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            scanf("%d",&a[i][j]);
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            for(st=j-1,dr=j+1;st>0 && dr<=m;st-- && dr++)
                if(a[i][st]==a[i][dr])
                    d[i][j]++;
                else
                    break;
    for(c=1;c<=m;c++)
        for(i=1;i<=n;i++)
        {
            vmin=d[i][c];sol=maxim(sol,2*d[i][c]+1);
            for(j=i+1;j<=n;j++)
            {
                vmin=minim(vmin,d[j][c]);
                sol=maxim(sol,(j-i+1)*(2*vmin+1));
            }
        }
    printf("%d\n",sol);
    return 0;
}