func_code_string: #include <bits/stdc++.h>   const long long N = 1000000;   using namespace std;   long long n, k, l, i = 0, j, mn, mx = N, ans = 0, als, r1, r2, r3, t, q, v, m,                      ii, r4;   string d1, d3, d2, s;   char kl, km, mk, lk;   double fg;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     ;     cin >> n;     bool a[N];     for (i = 0; i < n * 2; i++) {       cin >> t;       a[t - 1] = !a[t - 1];       m += a[t - 1] * 2 - 1;       ans = max(ans, m);     }     cout << ans;     return 0;   }   