import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc List<Integer> list = new ArrayList<>(); list new ArrayList<>() for (int i = 0; i < n; i++) list.add(sc.nextInt()); int i = 0; int i = 0; i 0 i < n i n i++ i++ i list.add(sc.nextInt()); list.add(sc.nextInt()) list.add list sc.nextInt() sc.nextInt sc Collections.sort(list) Collections.sort Collections list for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        } int i = 0; int i = 0; i 0 i < n-1 i n-1 n 1 i++ i++ i {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        } {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        } if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            } list.get(i).equals(list.get(i+1)) list.get(i).equals list.get(i) list.get list i list.get(i+1) list.get list i+1 i 1 {
              System.out.println("NO"); 
              return;
            } System.out.println("NO") System.out.println System.out System System.out "NO" return; System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) list.add(sc.nextInt());
        Collections.sort(list);

        for (int i = 0; i < n-1; i++) {
            if (list.get(i).equals(list.get(i+1))) {
              System.out.println("NO"); 
              return;
            }
        }
        System.out.println("YES");
    }
}