#include <bits/stdc++.h>
using namespace std;
ifstream fin("dreptpal.in");
ofstream fout("dreptpal.out");
const int NMAX = 1005;
int n, m, a[NMAX][NMAX], pal[NMAX][NMAX], st[NMAX], dr[NMAX], ans = -1;

int main()
{
    fin >> n >> m;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            fin >> a[i][j];
    for(int i = 1; i <= n; i++)
    {
        a[i][0] = 1e9 + 1;
        a[i][m + 1] = 1e9 - 1;
        for(int j = 1; j <= m; j++)
        {
            int st = j - 1, dr = j + 1;
            while(a[i][st] == a[i][dr])
                st--, dr++;
            pal[i][j] = dr - st - 1;
        }
    }
    for(int j = 1; j <= m; j++)
    {
        stack<int> stk;
        for(int i = 1; i <= n; i++)
        {
            while(!stk.empty() && pal[stk.top()][j] >= pal[i][j])
                stk.pop();
            st[i] = (stk.empty() ? 0 : stk.top());
            stk.push(i);
        }
        while(!stk.empty())
            stk.pop();
        for(int i = n; i >= 1; i--)
        {
            while(!stk.empty() && pal[stk.top()][j] >= pal[i][j])
                stk.pop();
            dr[i] = (stk.empty() ? n + 1 : stk.top());
            stk.push(i);
        }
        for(int i = 1; i <= n; i++)
            ans = max(ans, pal[i][j] * (dr[i] - st[i] - 1));
    }
    fout << ans;

    fin.close();
    fout.close();
    return 0;
}