import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int A[] = new int[N]; A new int[N] N for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			A[i] = sc.nextInt();
		} {
			A[i] = sc.nextInt();
		} A[i] = sc.nextInt() A[i] A i sc.nextInt() sc.nextInt sc sc.close() sc.close sc String ans = "YES"; ans "YES" Arrays.sort(A) Arrays.sort Arrays A for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		} int j = 1; int j = 1; j 1 j < N j N j++ j++ j {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		} {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		} if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			} A[j - 1] == A[j] A[j - 1] A j - 1 j 1 A[j] A j {
				ans = "NO";
				break;
			} ans = "NO" ans "NO" break; System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];

		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		sc.close();

		String ans = "YES";

		Arrays.sort(A);

		for (int j = 1; j < N; j++) {
			if (A[j - 1] == A[j]) {
				ans = "NO";
				break;
			}
		}
		System.out.println(ans);
	}
}
