func_code_string: #include <bits/stdc++.h>   #pragma GCC optimize( O3 )   using namespace std;   const int maxn = 403;   int n, m;   int a[maxn][maxn];   void read() {     cin >> n >> m;     for (int i = 1; i <= n; i++)       for (int j = 1; j <= m; j++) cin >> a[i][j];   }   int min_r[maxn];   long long s[maxn * maxn][7];   int find_first_bit(long long num) { return 63 - __builtin_clzll(num & -num); }   int find_last_bit(long long num) { return 63 - __builtin_clzll(num); }   int find_prev(int c, int idx) {     int pos = idx / 63;     idx %= 63;     long long left = (s[c][pos] & ((1ll << idx) - 1));     if (left) return pos * 63 + find_last_bit(left);     for (int i = pos - 1; i >= 0; i--)       if (s[c][i]) return i * 63 + find_last_bit(s[c][i]);     return -1;   }   int find_next(int c, int idx) {     int pos = idx / 63;     idx %= 63;     long long curr = (s[c][pos] >> (idx + 1));     if (curr) return pos * 63 + idx + 1 + find_first_bit(curr);     for (int i = pos + 1; i < 7; i++)       if (s[c][i]) return i * 63 + find_first_bit(s[c][i]);     return -1;   }   void solve() {     int ans = 0;     for (int i = 1; i <= n; i++) {       for (int j = 1; j <= m; j++) min_r[j] = m + 1;       for (int j = 1; j < maxn * maxn; j++)         for (int k = 0; k < 7; k++) s[j][k] = 0;       for (int j = i; j <= n; j++) {         for (int k = 1; k <= m; k++) {           int pos = (k - 1) / 63, r = (k - 1) % 63;           if (s[a[j][k]][pos] & (1ll << r))             min_r[k] = k;           else {             s[a[j][k]][pos] ^= (1ll << r);           }         }         for (int k = 1; k <= m; k++) {           int f1 = find_prev(a[j][k], k - 1), f2 = find_next(a[j][k], k - 1);           if (f1 != -1) min_r[f1 + 1] = min(min_r[f1 + 1], k);           if (f2 != -1) min_r[k] = min(min_r[k], f2 + 1);         }         int curr = m + 1;         for (int k = m; k >= 1; k--) {           curr = min(curr, min_r[k]);           ans = max(ans, (curr - k) * (j - i + 1));         }       }     }     cout << ans <<   n ;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(nullptr);     cout.tie(nullptr);     read();     solve();   }   