import java.util.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	} main {
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) HashMap<Integer, Integer> dict = new HashMap<>(); dict new HashMap<>() int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int Current; Current for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        } int i=0 ; int i=0 ; i 0 i<N i N i++ i++ i {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        } {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        } Current=sc.nextInt() Current sc.nextInt() sc.nextInt sc if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            } dict.containsKey(Current) dict.containsKey dict Current {
          		System.out.println("NO");
              	System.exit(0);
            } System.out.println("NO") System.out.println System.out System System.out "NO" System.exit(0) System.exit System 0 {
              	dict.put(Current, 1);              	
            } dict.put(Current, 1) dict.put dict Current 1 System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	}
} Main
import java.util.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	System.out.println("YES");
	}
}