TaskM

#include <iostream>
#include <set>

using namespace std;

int main()
{
    int n, x;
    cin >> n;
    set<int> s;
    for (int i = 0; i < n; i++)
    {
        cin >> x;
        s.insert(x);
    }
    if (s.size() == n)
        cout << "YES";
    else
        cout << "NO";
}