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

public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	}
		

} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	}
		

} Main public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	} main {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	} try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		} {
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		} Scanner scan = new Scanner(System.in) Scanner scan = new Scanner(System.in) new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int[] A  = new int[N]; A new int[N] N for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			} int i=0; int i=0; i 0 i<N i N i++ i++ i {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			} {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			} A[i] = scan.nextInt() A[i] A i scan.nextInt() scan.nextInt scan Arrays.sort(A) Arrays.sort Arrays A int ok = 1; ok 1 for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			} int k = 0; int k = 0; k 0 k<N-1 k N-1 N 1 k++ k++ k {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			} {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			} if(A[k] == A[k+1]) {	
					ok=0;
					break;
				} A[k] == A[k+1] A[k] A k A[k+1] A k+1 k 1 {	
					ok=0;
					break;
				} ok=0 ok 0 break; System.out.println(ok==1?"YES":"NO") System.out.println System.out System System.out ok==1?"YES":"NO" ok==1 ok 1 "YES" "NO" String[]args args public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	}
		

} public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	}
		

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

public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			int[] A  = new int[N];
			
			for(int i=0;i<N;i++) {
				A[i] = scan.nextInt();
				//System.out.println(A[i]);
			}
			
			
			Arrays.sort(A);
			int ok = 1;
			
			//System.out.println(N);
			for(int k = 0;k<N-1;k++) {
				//System.out.println("nono");
				
				if(A[k] == A[k+1]) {	
					ok=0;
					break;
				}
			}
			
			
			System.out.println(ok==1?"YES":"NO");
			

			
			
			
			
		}
		
		
	}
		

}
