import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    }
} import java.util.HashMap; HashMap java.util import java.util.Map; Map java.util import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    } main {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Map<Integer, Integer> map = new HashMap<>(); map new HashMap<>() for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        } {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        } int temp = Integer.parseInt(sc.next()); temp Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            } map.containsKey(temp) map.containsKey map temp {
                System.out.println("NO");
                return;
            } System.out.println("NO") System.out.println System.out System System.out "NO" return; {
                map.put(temp, 1);
            } map.put(temp, 1) map.put map temp 1 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 = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    }
} Main
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int temp = Integer.parseInt(sc.next());
            if (map.containsKey(temp)) {
                System.out.println("NO");
                return;
            } else {
                map.put(temp, 1);
            }
        }
        System.out.println("YES");
    }
}
