import java.util.HashSet;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	}

} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	}

} Main public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	} main {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	} Scanner scn = new Scanner(System.in); scn new Scanner(System.in) int N = scn.nextInt(); N scn.nextInt() scn.nextInt scn HashSet<Integer> arr = new HashSet<Integer>(); arr new HashSet<Integer>() boolean yes = true; yes true for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		} {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		} int a = scn.nextInt(); a scn.nextInt() scn.nextInt scn if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			} arr.contains(a) arr.contains arr a {
				yes = false;
				break;
			} yes = false yes false break; {
				arr.add(a);
			} arr.add(a) arr.add arr a System.out.println(yes ? "YES" : "NO") System.out.println System.out System System.out yes ? "YES" : "NO" yes "YES" "NO" String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	}

} public class Main {
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	}

} Main
import java.util.HashSet;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int N = scn.nextInt();
		HashSet<Integer> arr = new HashSet<Integer>();
		boolean yes = true;
		for (int i = 0; i < N; i++) {
			int a = scn.nextInt();
			if (arr.contains(a)) {
				yes = false;
				break;
			} else {
				arr.add(a);
			}
		}
		System.out.println(yes ? "YES" : "NO");
	}

}
