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();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			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();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			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();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int n= sc.nextInt();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			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 long[] a=new long[n]; a new long[n] n int count=0 count 0 flag=0; flag 0 for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			a[i]=sc.nextLong();
		} {
			a[i]=sc.nextLong();
		} a[i]=sc.nextLong() a[i] a i sc.nextLong() sc.nextLong sc Arrays.sort(a) Arrays.sort Arrays a for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				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=1;
				break;
			}
		} {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		} if(a[i]==a[i+1]) {
				flag=1;
				break;
			} a[i]==a[i+1] a[i] a i a[i+1] a i+1 i 1 {
				flag=1;
				break;
			} flag=1 flag 1 break; if(flag==0) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		} flag==0 flag 0 {
			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();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			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();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			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();
		long[] a=new long[n];
		int count=0,flag=0;
		for(int i=0;i<n;i++) {
			a[i]=sc.nextLong();
		}
		Arrays.sort(a);
		for(int i=0;i<n-1;i++) {
			if(a[i]==a[i+1]) {
				flag=1;
				break;
			}
		}
		if(flag==0) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}

}
