import java.util.Scanner;
import java.util.Arrays;
// import java.util.HashMap;
// import java.util.List;
// import java.util.ArrayList;
// import java.util.Map.Entry;
// import java.util.Comparator;
// import java.io.IOException;
// import java.io.InputStream;
// import java.util.NoSuchElementException;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    }
 
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    }
 
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc long A[] = new long[N]; A new long[N] N for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            A[i] = sc.nextLong();
        } {
            A[i] = sc.nextLong();
        } A[i] = sc.nextLong() A[i] A i sc.nextLong() sc.nextLong sc Arrays.sort(A) Arrays.sort Arrays A boolean ok = true; ok true for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        } int i = 0; int i = 0; i 0 i < N-1 i N-1 N 1 i++ i++ i {
            if(A[i] == A[i+1]) ok = false;
        } {
            if(A[i] == A[i+1]) ok = false;
        } if(A[i] == A[i+1]) ok = false; A[i] == A[i+1] A[i] A i A[i+1] A i+1 i 1 ok = false ok false if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        } ok {
            System.out.println("YES");
        } System.out.println("YES") System.out.println System.out System System.out "YES" {
            System.out.println("NO");
        } System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    }
 
} public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    }
 
} Main
import java.util.Scanner;
import java.util.Arrays;
// import java.util.HashMap;
// import java.util.List;
// import java.util.ArrayList;
// import java.util.Map.Entry;
// import java.util.Comparator;
// import java.io.IOException;
// import java.io.InputStream;
// import java.util.NoSuchElementException;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long A[] = new long[N];
        for(int i = 0; i < N; i++){
            A[i] = sc.nextLong();
        }
        Arrays.sort(A);
        boolean ok = true;
        for(int i = 0; i < N-1; i++){
            if(A[i] == A[i+1]) ok = false;
        }
        if(ok){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        




    }
 
}