import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    }

} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) throws Exception {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    }

} Main public static void main(String[] args) throws Exception {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    } main {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    } try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        } {
            int N = sc.nextInt();
            int[] A = new int[N];
            for (int i = 0; i < N; i++) {
                A[i] = sc.nextInt();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        } Scanner sc = new Scanner(System.in) Scanner sc = new Scanner(System.in) 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 Arrays.sort(A) Arrays.sort Arrays A for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            } int i = 1; int i = 1; i 1 i < A.length i A.length A A.length i++ i++ i {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            } {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            } if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                } A[i - 1] == A[i] A[i - 1] A i - 1 i 1 A[i] A i {
                    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) throws Exception {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    }

} public class Main {

    public static void main(String[] args) throws Exception {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    }

} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {
        try (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();
            }

            Arrays.sort(A);

            for (int i = 1; i < A.length; i++) {
                if (A[i - 1] == A[i]) {
                    System.out.println("NO");
                    return;
                }
            }

            System.out.println("YES");
        }
    }

}
