import java.util.*;

public class Main {

    Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    void run() {
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i=0; i<n; i++) arr[i] = sc.nextInt();

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    }

} import java.util.*; util.* java public class Main {

    Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    void run() {
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i=0; i<n; i++) arr[i] = sc.nextInt();

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    }

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

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    } run {
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i=0; i<n; i++) arr[i] = sc.nextInt();

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] arr = new int[n]; arr new int[n] n for (int i=0; i<n; i++) arr[i] = sc.nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i arr[i] = sc.nextInt(); arr[i] = sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc Arrays.sort(arr) Arrays.sort Arrays arr int cnt = 0; cnt 0 for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        } int i=0; int i=0; i 0 i<n-1 i n-1 n 1 i++ i++ i {
            if (arr[i]==arr[i+1]) cnt++;
        } {
            if (arr[i]==arr[i+1]) cnt++;
        } if (arr[i]==arr[i+1]) cnt++; arr[i]==arr[i+1] arr[i] arr i arr[i+1] arr i+1 i 1 cnt++ cnt if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        } cnt==0 cnt 0 {
            System.out.println("YES\n");
        } System.out.println("YES\n") System.out.println System.out System System.out "YES\n" {
            System.out.println("NO\n");
        } System.out.println("NO\n") System.out.println System.out System System.out "NO\n" public class Main {

    Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    void run() {
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i=0; i<n; i++) arr[i] = sc.nextInt();

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    }

} public class Main {

    Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    void run() {
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i=0; i<n; i++) arr[i] = sc.nextInt();

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    }

} Main
import java.util.*;

public class Main {

    Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Main().run();
    }

    void run() {
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i=0; i<n; i++) arr[i] = sc.nextInt();

        Arrays.sort(arr);

        int cnt = 0;

        for (int i=0; i<n-1; i++) {
            if (arr[i]==arr[i+1]) cnt++;
        }

        if (cnt==0) {
            System.out.println("YES\n");
        } else {
            System.out.println("NO\n");
        }

    }

}
