    import java.util.HashSet;
    import java.util.Scanner;
     
    public class Main {
    	public static void main(String[] args) {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	}
    } import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main {
    	public static void main(String[] args) {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	}
    } Main public static void main(String[] args) {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	} main {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan HashSet<Long> list = new HashSet<Long>(); list new HashSet<Long>() for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
    			list.add(scan.nextLong());
    		} {
    			list.add(scan.nextLong());
    		} list.add(scan.nextLong()) list.add list scan.nextLong() scan.nextLong scan if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		} n != list.size() n list.size() list.size list {
    			System.out.println("NO");
    		} System.out.println("NO") System.out.println System.out System System.out "NO" {
    			System.out.println("YES");
    		} 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) {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	}
    } public class Main {
    	public static void main(String[] args) {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	}
    } Main
    import java.util.HashSet;
    import java.util.Scanner;
     
    public class Main {
    	public static void main(String[] args) {
    		Scanner scan = new Scanner(System.in);
    		int n = scan.nextInt();
    		HashSet<Long> list = new HashSet<Long>();
     
    		for(int i = 0;i < n;i++) {
    			list.add(scan.nextLong());
    		}
     
    		if(n != list.size()) {
    			System.out.println("NO");
    		}else {
    			System.out.println("YES");
    		}
    	}
    }