#include <bits/stdc++.h>
using namespace std;
const int N = 400;
int f[N * N];
int dp[2][N][N];
int x[N][N];
int y[N][N * N];
int a[N][N];
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  memset(f, -1, sizeof f);
  memset(y, -1, sizeof y);
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      cin >> a[i][j];
      --a[i][j];
    }
  }
  int ans = 0;
  for (int i = 0; i < n; i++) {
    memset(f, -1, sizeof f);
    swap(dp[0], dp[1]);
    memset(dp[1], 0, sizeof dp[1]);
    for (int j = 0; j < m; j++) dp[1][j][0] = i + 1;
    for (int j = 0; j < m; j++) {
      int X = j + 1;
      for (int k = i; k >= 0; k--) {
        X = min(X, j - f[a[k][j]]);
        x[j][i - k + 1] = X;
      }
      f[a[i][j]] = j;
    }
    for (int j = 0; j < m; j++) {
      int W = -1;
      int ptr = i + 1;
      for (int len = 1; len <= j + 1; len++) {
        W = max(W, y[j - len + 1][a[i][j]]);
        int h = i - W;
        if (i) h = min(h, dp[0][j][len] + 1);
        if (j) h = min(h, dp[1][j - 1][len - 1]);
        if (!i && !j) h = 1;
        while (ptr && x[j][ptr] < len) {
          ptr--;
        }
        dp[1][j][len] = min(ptr, h);
        ans = max(ans, len * dp[1][j][len]);
      }
      y[j][a[i][j]] = i;
    }
  }
  cout << ans;
  return 0;
}
