Shared code

/*
  author: @ankingcodes
  created: 2021-07-18 09:12:58.312279
*/
        
#include<bits/stdc++.h>
#include<algorithm>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;
#define ll long long
#define MOD 1000000007

typedef tree<int, null_type, less<int>, rb_tree_tag,
                tree_order_statistics_node_update> PBDS;

typedef tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag,
                tree_order_statistics_node_update> pairPBDS;

void print(vector<ll> a) {
  cout << "VECTOR: ";for (auto x: a) cout << x << " "; cout << endl;
}

void print(set<ll> a) {
  cout << "SET: ";for (auto x: a) cout << x << " "; cout << endl;
}

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ll n; cin >> n;
  vector<ll> a(n);
  for (auto &i: a) cin >> i;
  if (a.size() == 1) {
    cout << 1 << endl;
    return 0;
  }
  ll i=0, j=-1;
  ll mx = INT_MIN;
  set<ll> s;
  for (int i=0;i<n;i++) {
    while (j < n-1 && !s.count(a[j+1])) s.insert(a[++j]);
    mx = max(mx, j - i + 1);
    s.erase(a[i]);
  }
  cout << mx << endl;
  return 0;
}