func_code_string: #include <bits/stdc++.h>   using namespace std;   int f[4005][4005];   int a[4005];   int main() {     int i, j, k, n, m = 0;     memset(f, 0, sizeof(f));     cin >> n;     for (i = 1; i <= n; i++) {       cin >> a[i];       k = 0;       for (j = 0; j < i; j++) {         f[i][j] = f[j][k] + 1;         if (a[j] == a[i]) {           k = j;         }         m = max(m, f[i][j]);       }     }     cout << m << endl;   }   