import java.util.*;
import java.io.PrintWriter;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} import java.util.*; util.* java import java.io.PrintWriter; PrintWriter java.io public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] a = new int[n]; a new int[n] n for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			a[i] = sc.nextInt();
		} {
			a[i] = sc.nextInt();
		} a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a) Arrays.sort Arrays a for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[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(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		} {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		} if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			} a[i] == a[i + 1] a[i] a i a[i + 1] a 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" String[] args args public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
} Main
import java.util.*;
import java.io.PrintWriter;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		for(int i = 0; i < n - 1; i++) {
			if(a[i] == a[i + 1]){
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
}