#include <bits/stdc++.h>
using namespace std;
const int N = 410;
int D[2][N][N], A[N][N], n, m;
int co[N * N], ans;
int main() {
  ios::sync_with_stdio(0);
  cin >> n >> m;
  for (int i = 1; i <= n; ++i)
    for (int j = 1; j <= m; ++j) cin >> A[i][j];
  for (int l1 = 1; l1 <= n; ++l1) {
    int v = ++co[A[l1][1]];
    for (int left = 1, p = 1; left <= m; ++left) {
      v = co[A[l1][p]];
      while (v < 2 && p <= m) {
        ++p;
        if (p <= m) v = ++co[A[l1][p]];
      }
      D[1][l1][left] = p;
      ans = max(ans, (D[1][l1][left] - left) * (l1 - l1 + 1));
      --co[A[l1][left]];
    }
  }
  for (int dif = 2; dif <= n; ++dif)
    for (int l = 1; l <= n - dif + 1; ++l) {
      int l1 = l;
      int l2 = l + dif - 1;
      int v1 = ++co[A[l1][1]];
      int v2 = ++co[A[l2][1]];
      for (int left = 1, p = 1; left <= m; ++left) {
        v1 = co[A[l1][p]];
        v2 = co[A[l2][p]];
        while (v1 < 2 && v2 < 2 && p <= m) {
          ++p;
          if (p <= m) v1 = ++co[A[l1][p]];
          if (p <= m) v2 = ++co[A[l2][p]];
        }
        D[dif & 1][l][left] = p;
        if (l1 <= l2 - 1)
          D[dif & 1][l][left] =
              min(D[dif & 1][l][left], D[(dif - 1) & 1][l][left]);
        if (l1 + 1 <= l2)
          D[dif & 1][l][left] =
              min(D[dif & 1][l][left], D[(dif - 1) & 1][l + 1][left]);
        ans = max(ans, (D[dif & 1][l][left] - left) * (l2 - l1 + 1));
        --co[A[l1][left]];
        --co[A[l2][left]];
      }
    }
  cout << ans << '\n';
}
