import java.util.*; 
import java.io.*; 

public class Main {
	public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	}
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
	public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	}
} Main public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	} main {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc HashSet<Integer> set = new HashSet<>(); set new HashSet<>() for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     } int i =0; int i =0; i 0 i<n i n i++ i++ i {
    	 set.add(sc.nextInt()); 
     } {
    	 set.add(sc.nextInt()); 
     } set.add(sc.nextInt()) set.add set sc.nextInt() sc.nextInt sc if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); set.size() == n set.size() set.size set n {
    	 System.out.println("YES");
     } System.out.println("YES") System.out.println System.out System System.out "YES" System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args public class Main {
	public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	}
} public class Main {
	public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	}
} Main
import java.util.*; 
import java.io.*; 

public class Main {
	public static void main(String[] args) throws IOException {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt(); 
     HashSet<Integer> set = new HashSet<>(); 
     for(int i =0; i<n; i++) {
    	 set.add(sc.nextInt()); 
     }
     if(set.size() == n) {
    	 System.out.println("YES");
     }
     else System.out.println("NO"); 
	}
}