import java.util.HashSet;
import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	}
 
} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util public class Main {
 
	public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	}
 
} Main public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	} main {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	} int n; n Scanner sc = new Scanner(System.in); sc new Scanner(System.in) n = sc.nextInt() n sc.nextInt() sc.nextInt sc HashSet<Integer> hs = new HashSet<Integer>(); hs new HashSet<Integer>() boolean flag = false; flag false String ans = ""; ans "" for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		} int i = 1; int i = 1; i 1 i <= n i n i++ i++ i {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		} {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		} int tmp = sc.nextInt(); tmp sc.nextInt() sc.nextInt sc if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			} hs.contains(tmp) hs.contains hs tmp {
				flag = true;
				break;
			} flag = true flag true break; {
				hs.add(tmp);
			} hs.add(tmp) hs.add hs tmp if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		} flag {
			ans = "NO";
		} ans = "NO" ans "NO" {
			ans = "YES";
		} ans = "YES" ans "YES" System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
 
	public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	}
 
} public class Main {
 
	public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	}
 
} Main
import java.util.HashSet;
import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		System.out.println(ans);
 
	}
 
}