

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
	    Scanner sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    }
} import java.lang.reflect.Array; Array java.lang.reflect import java.util.ArrayList; ArrayList java.util import java.util.HashMap; HashMap java.util import java.util.Map; Map java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
	    Scanner sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    }
} Main public static void main(String[] args) {
	    Scanner sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    } main {
	    Scanner sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    } Scanner sin=new Scanner(System.in); sin new Scanner(System.in) int n=sin.nextInt(); n sin.nextInt() sin.nextInt sin Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>(); mp new HashMap<Integer, Boolean>() boolean k=false; k false for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		} {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		} int data = sin.nextInt(); data sin.nextInt() sin.nextInt sin if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true); mp.containsKey(data) mp.containsKey mp data {
				k=true;
			} k=true k true mp.put(data,true) mp.put mp data true if(k) System.out.println("NO");
		else System.out.println("YES"); k System.out.println("NO") System.out.println System.out System System.out "NO" 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 sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    }
} public class Main {
    public static void main(String[] args) {
	    Scanner sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    }
} Main


import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
	    Scanner sin=new Scanner(System.in);
	    int n=sin.nextInt();
		Map<Integer,Boolean> mp=new HashMap<Integer, Boolean>();
	    boolean k=false;
		for (int i = 0; i < n; i++) {
			int data = sin.nextInt();
			if(mp.containsKey(data)){
				k=true;
			}else mp.put(data,true);
		}
		if(k) System.out.println("NO");
		else System.out.println("YES");
    }
}
