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

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

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