1. Unique Elements

#include <bits/stdc++.h>

using namespace std ;
#define sz(s) int(s.size())
#define all(s) s.begin() , s.end()
#define imin INT_MIN
#define imax INT_MAX
#define ll long long
#define ull unsigned long long
#define Time cerr << "Time Taken: " << (float)clock() / CLOCKS_PER_SEC << " Secs" << "\n";
#define cin(v) for (auto& i : v) cin >> i ;
#define pb(x) push_back(x)
#define getline(s) getline(cin >> ws, s)
#define Mod 1'000'000'007
#define INF 2'000'000'000
#define Num_of_Digits(n) ((int)log10(n)+1)

void ABDEL3AL () {
    ios_base::sync_with_stdio(false); cin.tie(nullptr) , cout.tie(nullptr) ;
#ifndef ONLINE_JUDGE
    freopen("input.txt" , "r" , stdin) , freopen("output.txt" , "w" , stdout) ;
#endif
    Time
}


int main() {
    ABDEL3AL() ;
    int n ; cin >> n ;
    vector <ll> v(n) ;
    cin(v) ;
    sort (all(v)) ;
    for (int i = 1; i < n; i++) {
        if (v[i] == v[i - 1]) v.erase(remove(v.begin() , v.end() , v[i]), v.end());
    }
    cout << sz(v) ;
    return 0;
}