import java.io.*;
import java.util.Arrays;
import java.util.*;
public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	}
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		public String nextLine() throws IOException {
			return br.readLine();
		}
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException {
			return br.ready();
		}
	}
} import java.io.*; io.* java import java.util.Arrays; Arrays java.util import java.util.*; util.* java public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	}
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		public String nextLine() throws IOException {
			return br.readLine();
		}
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException {
			return br.ready();
		}
	}
} Main public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	} main {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) PrintWriter pw = new PrintWriter(System.out); pw new PrintWriter(System.out) int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] num=new int[n]; num new int[n] n boolean x=true; x true for(int i=0;i<n;i++)
			num[i]=sc.nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i num[i]=sc.nextInt(); num[i]=sc.nextInt() num[i] num i sc.nextInt() sc.nextInt sc Arrays.sort(num) Arrays.sort Arrays num for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		} int i=0; int i=0; i 0 i<n-1 i n-1 n 1 i++ i++ i {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		} {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		} if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			} num[i]==num[i+1] num[i] num i num[i+1] num i+1 i 1 {
				pw.print("NO");
				x=false;
				break;
			} pw.print("NO") pw.print pw "NO" x=false x false break; if(x)
		  pw.print("YES"); x pw.print("YES") pw.print pw "YES" pw.close() pw.close pw String[] args args static class Scanner {
		StringTokenizer st;
		BufferedReader br;
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		public String nextLine() throws IOException {
			return br.readLine();
		}
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException {
			return br.ready();
		}
	} Scanner StringTokenizer st; st BufferedReader br; br public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		} Scanner {
			br = new BufferedReader(new InputStreamReader(s));
		} br = new BufferedReader(new InputStreamReader(s)) br new BufferedReader(new InputStreamReader(s)) InputStream s s public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		} Scanner {
			br = new BufferedReader(new FileReader(file));
		} br = new BufferedReader(new FileReader(file)) br new BufferedReader(new FileReader(file)) String file file public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		} next {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		} while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine()); st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st public int nextInt() throws IOException {
			return Integer.parseInt(next());
		} nextInt {
			return Integer.parseInt(next());
		} return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next public long nextLong() throws IOException {
			return Long.parseLong(next());
		} nextLong {
			return Long.parseLong(next());
		} return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public String nextLine() throws IOException {
			return br.readLine();
		} nextLine {
			return br.readLine();
		} return br.readLine(); br.readLine() br.readLine br public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		} nextDouble {
			return Double.parseDouble(next());
		} return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public boolean ready() throws IOException {
			return br.ready();
		} ready {
			return br.ready();
		} return br.ready(); br.ready() br.ready br public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	}
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		public String nextLine() throws IOException {
			return br.readLine();
		}
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException {
			return br.ready();
		}
	}
} public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	}
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		public String nextLine() throws IOException {
			return br.readLine();
		}
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException {
			return br.ready();
		}
	}
} Main
import java.io.*;
import java.util.Arrays;
import java.util.*;
public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int n=sc.nextInt();
		int[] num=new int[n];
		boolean x=true;
		for(int i=0;i<n;i++)
			num[i]=sc.nextInt();
		Arrays.sort(num);
		for(int i=0;i<n-1;i++) {
			if(num[i]==num[i+1]) {
				pw.print("NO");
				x=false;
				break;
			}
		}
		if(x)
		  pw.print("YES");
		pw.close();
	}
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		public String nextLine() throws IOException {
			return br.readLine();
		}
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
		public boolean ready() throws IOException {
			return br.ready();
		}
	}
}