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

public class Main {

	public static void main(String[] args) {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	}
} Main public static void main(String[] args) {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	} main {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	} Scanner scan = new Scanner(System.in); scan 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();
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			a[i]=scan.nextInt();
		} {
			a[i]=scan.nextInt();
		} a[i]=scan.nextInt() a[i] a i scan.nextInt() scan.nextInt scan scan.close() scan.close scan Arrays.sort(a) Arrays.sort Arrays a int check=0; check 0 for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		} {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		} for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			} int j=i+1; int j=i+1; j i+1 i 1 j<n j n j++ j++ j {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			} {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			} if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				} i!=j i j {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				} if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					} a[i]==a[j] a[i] a i a[j] a j {
						check=1;
						break;
					} check=1 check 1 break; {
						break;
					} break; if(check==1)break; check==1 check 1 break; System.out.println((check==1)? "NO":"YES") System.out.println System.out System System.out (check==1)? "NO":"YES" (check==1) check 1 "NO" "YES" String[] args args public class Main {

	public static void main(String[] args) {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	}
} public class Main {

	public static void main(String[] args) {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		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();
		}
		scan.close();
		Arrays.sort(a);

		int check=0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				if(i!=j) {
					if(a[i]==a[j]) {
						check=1;
						break;
					}else {
						break;
					}
				}
			}
			if(check==1)break;
		}
		System.out.println((check==1)? "NO":"YES");
	}
}