#include <bits/stdc++.h>
using namespace std;
const int MAXN = 404;
const int MAXK = MAXN * MAXN;
short f[2][MAXN][MAXN];
int bio[2][MAXK], last[2][MAXK];
int a[MAXN][MAXN];
enum { L, R };
int main(void) {
  int n, m;
  scanf("%d %d", &n, &m);
  for (int i = 0; i < (n); ++i)
    for (int j = 0; j < (m); ++j) scanf("%d", a[i] + j);
  int ans = 0, cookie = 0;
  for (int d = 0; d < (m); ++d) {
    int now = d & 1, prev = now ^ 1;
    for (int y1 = 0; y1 < (m - d); ++y1) {
      int y2 = y1 + d;
      cookie++;
      for (int x1 = n - 1; x1 >= 0; --x1) {
        short &ref = f[now][x1][y1];
        ref = n - 1;
        if (y1 < y2) ref = min(f[prev][x1][y1 + 1], f[prev][x1][y1]);
        if (x1 + 1 < n) ref = min(ref, f[now][x1 + 1][y1]);
        if (bio[R][a[x1][y1]] == cookie)
          ref = min(ref, short(last[R][a[x1][y1]] - 1));
        if (bio[L][a[x1][y2]] == cookie)
          ref = min(ref, short(last[L][a[x1][y2]] - 1));
        if (y1 < y2 && a[x1][y1] == a[x1][y2]) ref = x1 - 1;
        bio[L][a[x1][y1]] = cookie, last[L][a[x1][y1]] = x1;
        bio[R][a[x1][y2]] = cookie, last[R][a[x1][y2]] = x1;
        ans = max(ans, (y2 - y1 + 1) * (ref - x1 + 1));
      }
    }
  }
  printf("%d\n", ans);
  return 0;
}
