import java.util.*;
import java.math.*;
public class Main {
	static int x;
	static int ans;
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	}
}  import java.util.*; util.* java import java.math.*; math.* java public class Main {
	static int x;
	static int ans;
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	}
} Main static int x; x static int ans; ans public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	} main {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	} Scanner in = new Scanner(System.in); in new Scanner(System.in) int n = in.nextInt(); n in.nextInt() in.nextInt in Set<Integer> st = new TreeSet<>(); st new TreeSet<>() for(int i = 0; i < n; i++) st.add(in.nextInt()); int i = 0; int i = 0; i 0 i < n i n i++ i++ i st.add(in.nextInt()); st.add(in.nextInt()) st.add st in.nextInt() in.nextInt in if(st.size() == n) System.out.println("YES");
		else System.out.println("NO"); st.size() == n st.size() st.size st n 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 {
	static int x;
	static int ans;
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	}
} public class Main {
	static int x;
	static int ans;
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	}
} Main
import java.util.*;
import java.math.*;
public class Main {
	static int x;
	static int ans;
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Set<Integer> st = new TreeSet<>();
		for(int i = 0; i < n; i++) st.add(in.nextInt());
		if(st.size() == n) System.out.println("YES");
		else System.out.println("NO");
	}
} 
