import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] A = new int[N]; A new int[N] N for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            A[i] = sc.nextInt();
        } {
            A[i] = sc.nextInt();
        } A[i] = sc.nextInt() A[i] A i sc.nextInt() sc.nextInt sc String ans = "YES"; ans "YES" Arrays.sort(A) Arrays.sort Arrays A int tmp = 0; tmp 0 for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        } {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        } if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            } tmp == A[i] tmp A[i] A i {
                ans = "NO";
                break;
            } ans = "NO" ans "NO" break; {
                tmp = A[i];
            } tmp = A[i] tmp A[i] A i System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = sc.nextInt();
        }

        String ans = "YES";
        Arrays.sort(A);
        int tmp = 0;
        for (int i = 0; i < N; i++) {
            if(tmp == A[i]){
                ans = "NO";
                break;
            }else{
                tmp = A[i];
            }
        }

        System.out.println(ans);
    }
}
