import java.util.HashSet;
import java.util.Scanner;


// 137_b
public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    }

    /*
     * 以下メソッド集
     */

    static long gcd(long a, long b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static int gcd(int a, int b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static void out(String info) {

        System.out.println(info);
    }

    static void out(int info) {

        System.out.println(info);
    }

    static void out(double info) {

        System.out.println(info);
    }

    static void out(long info) {

        System.out.println(info);
    }

} import java.util.HashSet; HashSet 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 = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    }

    /*
     * 以下メソッド集
     */

    static long gcd(long a, long b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static int gcd(int a, int b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static void out(String info) {

        System.out.println(info);
    }

    static void out(int info) {

        System.out.println(info);
    }

    static void out(double info) {

        System.out.println(info);
    }

    static void out(long info) {

        System.out.println(info);
    }

} Main public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    } main {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc HashSet<Long> hs = new HashSet<>(); hs new HashSet<>() for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            hs.add(sc.nextLong());
        } {
            hs.add(sc.nextLong());
        } hs.add(sc.nextLong()) hs.add hs sc.nextLong() sc.nextLong sc String ans = hs.size() == n ? "YES" : "NO"; ans hs.size() == n ? "YES" : "NO" hs.size() == n hs.size() hs.size hs n "YES" "NO" out(ans) out ans String[] args args static long gcd(long a, long b) {

        return (b == 0) ? a : gcd(b, a % b);
    } gcd {

        return (b == 0) ? a : gcd(b, a % b);
    } return (b == 0) ? a : gcd(b, a % b); (b == 0) ? a : gcd(b, a % b) (b == 0) b 0 a gcd(b, a % b) gcd b a % b a b long a a long b b static int gcd(int a, int b) {

        return (b == 0) ? a : gcd(b, a % b);
    } gcd {

        return (b == 0) ? a : gcd(b, a % b);
    } return (b == 0) ? a : gcd(b, a % b); (b == 0) ? a : gcd(b, a % b) (b == 0) b 0 a gcd(b, a % b) gcd b a % b a b int a a int b b static void out(String info) {

        System.out.println(info);
    } out {

        System.out.println(info);
    } System.out.println(info) System.out.println System.out System System.out info String info info static void out(int info) {

        System.out.println(info);
    } out {

        System.out.println(info);
    } System.out.println(info) System.out.println System.out System System.out info int info info static void out(double info) {

        System.out.println(info);
    } out {

        System.out.println(info);
    } System.out.println(info) System.out.println System.out System System.out info double info info static void out(long info) {

        System.out.println(info);
    } out {

        System.out.println(info);
    } System.out.println(info) System.out.println System.out System System.out info long info info public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    }

    /*
     * 以下メソッド集
     */

    static long gcd(long a, long b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static int gcd(int a, int b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static void out(String info) {

        System.out.println(info);
    }

    static void out(int info) {

        System.out.println(info);
    }

    static void out(double info) {

        System.out.println(info);
    }

    static void out(long info) {

        System.out.println(info);
    }

} public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    }

    /*
     * 以下メソッド集
     */

    static long gcd(long a, long b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static int gcd(int a, int b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static void out(String info) {

        System.out.println(info);
    }

    static void out(int info) {

        System.out.println(info);
    }

    static void out(double info) {

        System.out.println(info);
    }

    static void out(long info) {

        System.out.println(info);
    }

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


// 137_b
public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        HashSet<Long> hs = new HashSet<>();

        for (int i = 0; i < n; i++) {
            hs.add(sc.nextLong());
        }

        String ans = hs.size() == n ? "YES" : "NO";

        out(ans);

    }

    /*
     * 以下メソッド集
     */

    static long gcd(long a, long b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static int gcd(int a, int b) {

        return (b == 0) ? a : gcd(b, a % b);
    }

    static void out(String info) {

        System.out.println(info);
    }

    static void out(int info) {

        System.out.println(info);
    }

    static void out(double info) {

        System.out.println(info);
    }

    static void out(long info) {

        System.out.println(info);
    }

}
