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

public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	}

} import java.util.HashSet; HashSet java.util import java.util.Scanner; Scanner java.util import java.util.Set; Set java.util public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	}

} Main public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	} main {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long n = sc.nextLong(); n sc.nextLong() sc.nextLong sc Set<Long> numSet = new HashSet<>(); numSet new HashSet<>() boolean hasSame = false; hasSame false for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		} {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		} Long num = sc.nextLong(); num sc.nextLong() sc.nextLong sc if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			} numSet.contains(num) numSet.contains numSet num {
				hasSame = true;
				break;
			} hasSame = true hasSame true break; {
				numSet.add(num);
			} numSet.add(num) numSet.add numSet num System.out.println(hasSame ? "NO" : "YES") System.out.println System.out System System.out hasSame ? "NO" : "YES" hasSame "NO" "YES" sc.close() sc.close sc String[] args args public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	}

} public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	}

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

public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "YES");
		sc.close();
	}

}