#include <bits/stdc++.h>

using namespace std;

vector<int> q;
int up[1010],down[1010],d[1010][1010],v[1010][1010];

int main()
{
    freopen("dreptpal.in","r",stdin);
    freopen("dreptpal.out","w",stdout);
    int n,m,sol=0;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++) scanf("%d",&v[i][j]);
    for(int i=1;i<=n;i++)
    {
        int l=0,poz=0;
        for(int j=1;j<=m;j++)
        {
            if(j+d[i][j]<poz+l) d[i][j]=min(poz+l-j,d[i][2*poz-j]);
            if(j+d[i][j]>=poz+l) while(j+d[i][j]<m && j-d[i][j]>1 && v[i][j+d[i][j]+1]==v[i][j-d[i][j]-1]) d[i][j]++;
            if(j+d[i][j]>poz+l) {poz=j;l=d[i][j];}
        }
        for(int j=1;j<=m;j++) d[i][j]=2*d[i][j]+1;
    }
    for(int i=1;i<=m;i++)
    {
        q.push_back(0);
        memset(up,0,sizeof(up));
        memset(down,0,sizeof(down));
        for(int j=1;j<=n;j++)
        {
            while(d[j][i]<=v[q.back()][i]) {down[q.back()]=j;q.pop_back();}
            up[j]=q.back();
            q.push_back(j);
        }
        q.clear();
        for(int j=1;j<=n;j++)
        {
            if(down[j]==0) down[j]=n+1;
            sol=max(sol,(down[j]-up[j]-1)*d[j][i]);
        }
    }
    printf("%d",sol);
    return 0;
}