Unique Elements

    1#include <bits/stdc++.h>
    2 
    3using namespace std;
    4 
    5#define f first
    6#define s second
    7#define pb push_back
    8#define eb emplace_back
    9#define mp make_pair
    10 
    11typedef long long ll;
    12const int INF = 0x3f3f3f3f;
    13//#define int long long 
    14 
    15int main() {
    16    ios::sync_with_stdio(0);
    17    cin.tie(0); 
    18    int n;
    19    cin >> n;
    20    unordered_set<int>s;
    21    for(int i = 0; i < n; i++){
    22        int x; cin >> x;
    23        s.insert(x);
    24    }
    25    cout << s.size() << '\n';
    26    return 0;
    27}
    28