#include <bits/stdc++.h>
using namespace std;
const long long LINF = 1e18 + 5;
const int MOD = (int)1e9 + 7;
const int LOG = 25;
const int INF = 1e6;
const int N = 4e2 + 5;
const int M = 12;
const int SQ = 350;
int n, m, ans, a[N][N], dp[N][N];
short int up[N * N][N];
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) scanf("%d", &a[i][j]);
  for (int i = 1; i <= n; i++)
    for (int ln = 1; ln <= m; ln++)
      for (int l = 1; l <= m - ln + 1; l++) {
        int r = l + ln - 1;
        if (l == r) {
          dp[l][r] = max(dp[l][r], up[a[i][l]][l] + 1);
          up[a[i][l]][l] = i;
        } else {
          dp[l][r] = max(dp[l][r], dp[l + 1][r]);
          dp[l][r] = max(dp[l][r], dp[l][r - 1]);
          dp[l][r] = max(dp[l][r], up[a[i][l]][r] + 1);
          dp[l][r] = max(dp[l][r], up[a[i][r]][l] + 1);
        }
        ans = max(ans, (i - dp[l][r] + 1) * ln);
      }
  printf("%d\n", ans);
}
