#include <bits/stdc++.h>
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using namespace std;
const int N = 402;
int n, m, mxR[N], nL[N][N], nR[N][N], a[N][N], lst[N * N];
vector<int> com;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> n >> m;
  for (int i = (1); i <= (n); ++i)
    for (int j = (1); j <= (m); ++j)
      cin >> a[i][j], com.emplace_back(a[i][j]), nL[i][j] = 0, nR[i][j] = N;
  sort((com).begin(), (com).end());
  com.erase(unique((com).begin(), (com).end()), com.end());
  for (int i = (1); i <= (n); ++i)
    for (int j = (1); j <= (m); ++j)
      a[i][j] = lower_bound((com).begin(), (com).end(), a[i][j]) - com.begin();
  mxR[m + 1] = m;
  int ans = 0;
  for (int up = (n); up >= (1); --up) {
    for (int i = (1); i <= (m); ++i) {
      mxR[i] = m;
      if (lst[a[up][i]]) nL[up][i] = max(nL[up][i], lst[a[up][i]]);
      lst[a[up][i]] = i;
      for (int j = (up + 1); j <= (n); ++j)
        if (lst[a[j][i]]) nL[j][i] = max(nL[j][i], lst[a[j][i]]);
    }
    for (int i = (1); i <= (m); ++i) lst[a[up][i]] = 0;
    for (int i = (m); i >= (1); --i) {
      if (lst[a[up][i]]) nR[up][i] = min(nR[up][i], lst[a[up][i]]);
      lst[a[up][i]] = i;
      for (int j = (up + 1); j <= (n); ++j)
        if (lst[a[j][i]]) nR[j][i] = min(nR[j][i], lst[a[j][i]]);
    }
    for (int i = (1); i <= (m); ++i) lst[a[up][i]] = 0;
    for (int down = (up); down <= (n); ++down) {
      for (int i = (m); i >= (1); --i) {
        mxR[i] = min(mxR[i], mxR[i + 1]);
        if (nL[down][i] > 0) mxR[nL[down][i]] = min(mxR[nL[down][i]], i - 1);
        if (nR[down][i] < N) mxR[i] = min(mxR[i], nR[down][i] - 1);
        ans = max(ans, (down - up + 1) * (mxR[i] - i + 1));
      }
    }
  }
  cout << ans;
  return 0;
}
