import java.util.*;
public class Main {
	public static void main(String[] args){
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
      	
		
      	
    }
		
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
      	
		
      	
    }
		
} Main public static void main(String[] args){
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
      	
		
      	
    } main {
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			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 int num_arr[] = new int[N]; num_arr new int[N] N boolean flag = true; flag true for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < num_arr.length i num_arr.length num_arr num_arr.length i++ i++ i {
			num_arr[i] = sc.nextInt();
		} {
			num_arr[i] = sc.nextInt();
		} num_arr[i] = sc.nextInt() num_arr[i] num_arr i sc.nextInt() sc.nextInt sc Arrays.sort(num_arr) Arrays.sort Arrays num_arr for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		} int i = 0; int i = 0; i 0 i < num_arr.length-1 i num_arr.length-1 num_arr.length num_arr num_arr.length 1 i++ i++ i {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		} {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		} if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			} num_arr[i] ==num_arr[i+1] num_arr[i] num_arr i num_arr[i+1] num_arr i+1 i 1 {
				flag = false;
				break;
			} flag = false flag false break; if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		} flag {
			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);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
      	
		
      	
    }
		
} public class Main {
	public static void main(String[] args){
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
      	
		
      	
    }
		
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
      	
		
      	
    }
		
}