
import java.util.*;
public class Main {
	public static void main(String[] args) {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args) {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	}
} Main public static void main(String[] args) {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	} main {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	} Scanner input = new Scanner(System.in); input new Scanner(System.in) int n = input.nextInt(); n input.nextInt() input.nextInt input int [] a = new int[n]; a new int[n] n for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n ++i ++i i {
			a[i] = input.nextInt();
		} {
			a[i] = input.nextInt();
		} a[i] = input.nextInt() a[i] a i input.nextInt() input.nextInt input Arrays.sort(a) Arrays.sort Arrays a boolean status = true; status true for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		} int i = 0; int i = 0; i 0 i < n - 1 i n - 1 n 1 ++i ++i i {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		} {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		} if(a[i] == a[i + 1]) {
				status = false;
				break;
			} a[i] == a[i + 1] a[i] a i a[i + 1] a i + 1 i 1 {
				status = false;
				break;
			} status = false status false break; String answer = "YES"; answer "YES" if(!status) {
			answer = "NO";
		} !status status {
			answer = "NO";
		} answer = "NO" answer "NO" System.out.println(answer) System.out.println System.out System System.out answer input.close() input.close input String[] args args public class Main {
	public static void main(String[] args) {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	}
} public class Main {
	public static void main(String[] args) {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	}
} Main

import java.util.*;
public class Main {
	public static void main(String[] args) {
		
		Scanner input = new Scanner(System.in);
		int n = input.nextInt();
		int [] a = new int[n];
		for(int i = 0; i < n; ++i) {
			a[i] = input.nextInt();
		}
		Arrays.sort(a);
		boolean status = true;
		for(int i = 0; i < n - 1; ++i) {
			if(a[i] == a[i + 1]) {
				status = false;
				break;
			}
		}
		String answer = "YES";
		if(!status) {
			answer = "NO";
		}
		System.out.println(answer);
		input.close();	
	}
}
