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

class Main{
    public static void main(String args[]){
        Scanner str = new Scanner(System.in);
        int N = str.nextInt();
        int NList[] = new int[N];

        for(int i = 0; i < N; i++){
            NList[i] = str.nextInt();
        }

        Arrays.sort(NList);

        for(int i = 0; i < N - 1; i++){
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        }

        System.out.println("YES");
        return;
    }
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util class Main{
    public static void main(String args[]){
        Scanner str = new Scanner(System.in);
        int N = str.nextInt();
        int NList[] = new int[N];

        for(int i = 0; i < N; i++){
            NList[i] = str.nextInt();
        }

        Arrays.sort(NList);

        for(int i = 0; i < N - 1; i++){
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        }

        System.out.println("YES");
        return;
    }
} Main public static void main(String args[]){
        Scanner str = new Scanner(System.in);
        int N = str.nextInt();
        int NList[] = new int[N];

        for(int i = 0; i < N; i++){
            NList[i] = str.nextInt();
        }

        Arrays.sort(NList);

        for(int i = 0; i < N - 1; i++){
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        }

        System.out.println("YES");
        return;
    } main {
        Scanner str = new Scanner(System.in);
        int N = str.nextInt();
        int NList[] = new int[N];

        for(int i = 0; i < N; i++){
            NList[i] = str.nextInt();
        }

        Arrays.sort(NList);

        for(int i = 0; i < N - 1; i++){
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        }

        System.out.println("YES");
        return;
    } Scanner str = new Scanner(System.in); str new Scanner(System.in) int N = str.nextInt(); N str.nextInt() str.nextInt str int NList[] = new int[N]; NList new int[N] N for(int i = 0; i < N; i++){
            NList[i] = str.nextInt();
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            NList[i] = str.nextInt();
        } {
            NList[i] = str.nextInt();
        } NList[i] = str.nextInt() NList[i] NList i str.nextInt() str.nextInt str Arrays.sort(NList) Arrays.sort Arrays NList for(int i = 0; i < N - 1; i++){
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        } int i = 0; int i = 0; i 0 i < N - 1 i N - 1 N 1 i++ i++ i {
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        } {
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        } if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            } NList[i] == NList[i + 1] NList[i] NList i NList[i + 1] NList i + 1 i 1 {
                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" return; String args[] args
import java.util.Arrays;
import java.util.Scanner;

class Main{
    public static void main(String args[]){
        Scanner str = new Scanner(System.in);
        int N = str.nextInt();
        int NList[] = new int[N];

        for(int i = 0; i < N; i++){
            NList[i] = str.nextInt();
        }

        Arrays.sort(NList);

        for(int i = 0; i < N - 1; i++){
            if(NList[i] == NList[i + 1]){
                System.out.println("NO");
                return;
            }
        }

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