import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
	int n =  sc.nextInt();
	List<String> a = new ArrayList<String>();

	for(int i=0;i<n;i++) {
		a.add(sc.next());
	}

	List<String> b = new ArrayList<String>(new HashSet<>(a));

	int la = a.size();
	int lb = b.size();
	System.out.println(la==lb?"YES":"NO");
  }
} import java.util.ArrayList; ArrayList java.util import java.util.HashSet; HashSet java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
	int n =  sc.nextInt();
	List<String> a = new ArrayList<String>();

	for(int i=0;i<n;i++) {
		a.add(sc.next());
	}

	List<String> b = new ArrayList<String>(new HashSet<>(a));

	int la = a.size();
	int lb = b.size();
	System.out.println(la==lb?"YES":"NO");
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
	int n =  sc.nextInt();
	List<String> a = new ArrayList<String>();

	for(int i=0;i<n;i++) {
		a.add(sc.next());
	}

	List<String> b = new ArrayList<String>(new HashSet<>(a));

	int la = a.size();
	int lb = b.size();
	System.out.println(la==lb?"YES":"NO");
  } main {
    Scanner sc = new Scanner(System.in);
	int n =  sc.nextInt();
	List<String> a = new ArrayList<String>();

	for(int i=0;i<n;i++) {
		a.add(sc.next());
	}

	List<String> b = new ArrayList<String>(new HashSet<>(a));

	int la = a.size();
	int lb = b.size();
	System.out.println(la==lb?"YES":"NO");
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n =  sc.nextInt(); n sc.nextInt() sc.nextInt sc List<String> a = new ArrayList<String>(); a new ArrayList<String>() for(int i=0;i<n;i++) {
		a.add(sc.next());
	} int i=0; int i=0; i 0 i<n i n i++ i++ i {
		a.add(sc.next());
	} {
		a.add(sc.next());
	} a.add(sc.next()) a.add a sc.next() sc.next sc List<String> b = new ArrayList<String>(new HashSet<>(a)); b new ArrayList<String>(new HashSet<>(a)) int la = a.size(); la a.size() a.size a int lb = b.size(); lb b.size() b.size b System.out.println(la==lb?"YES":"NO") System.out.println System.out System System.out la==lb?"YES":"NO" la==lb la lb "YES" "NO" String[] args args
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
	int n =  sc.nextInt();
	List<String> a = new ArrayList<String>();

	for(int i=0;i<n;i++) {
		a.add(sc.next());
	}

	List<String> b = new ArrayList<String>(new HashSet<>(a));

	int la = a.size();
	int lb = b.size();
	System.out.println(la==lb?"YES":"NO");
  }
}