#include <fstream>
#include <algorithm>

using namespace std;

ifstream cin("dreptpal.in");
ofstream cout("dreptpal.out");

const int MAXN = 1000;

int a[1 + MAXN][1 + MAXN], pal[1 + MAXN][1 + MAXN], pi[1 + MAXN], length[1 + MAXN];

void Manacher(int n, int m) {
    for (int i = 1; i <= n; i++) {
        int l = 0, r = 0;
        for (int j = 1; j <= m; j++) {
            if (j <= r)
                pal[i][j] = min(pal[i][2 * l - j], r - j);
            while (j - pal[i][j] > 1 && j + pal[i][j] < m && a[i][j - pal[i][j] - 1] == a[i][j + pal[i][j] + 1])
                pal[i][j]++;
            if (j + pal[i][j] > r) {
                r = j + pal[i][j];
                l = j;
            }
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            cin >> a[i][j];
    Manacher(n, m);
    int answer = 0;
    for (int j = 1; j <= m; j++) {
        for (int i = 1; i <= n; i++) {
            int k = i - 1;
            while (k >= 1 && pal[k][j] >= pal[i][j])
                k = pi[k];
            pi[i] = k;
            length[i] = i - k;
        }
        for (int i = n; i >= 1; i--) {
            int k = i + 1;
            while (k <= n && pal[k][j] >= pal[i][j])
                k = pi[k];
            pi[i] = k;
            length[i] = length[i] + k - i;
        }
        for (int i = 1; i <= n; i++)
            answer = max(answer, (length[i] - 1) * (2 * pal[i][j] + 1));
    }
    cout << answer << "\n";
    return 0;
}