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();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	}
} 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();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N =  sc.nextInt();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	} main {
		Scanner sc = new Scanner(System.in);
		int N =  sc.nextInt();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N =  sc.nextInt(); N sc.nextInt() sc.nextInt sc long A[] = new long[N]; A new long[N] N for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		} int i=0; int i=0; i 0 i<N i N i++ i++ i {
			A[i] = sc.nextLong();
		} {
			A[i] = sc.nextLong();
		} A[i] = sc.nextLong() A[i] A i sc.nextLong() sc.nextLong sc Arrays.parallelSort(A) Arrays.parallelSort Arrays A for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		} int i=1; int i=1; i 1 i<N i N i++ i++ i {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		} {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		} if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			} A[i]==A[i-1] A[i] A i A[i-1] A i-1 i 1 {
				System.out.print("NO");
				return ;
			} System.out.print("NO") System.out.print System.out System System.out "NO" return ; System.out.print("YES") System.out.print System.out System System.out "YES" return ; String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N =  sc.nextInt();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N =  sc.nextInt();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	}
} 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();
		long A[] = new long[N];
		for(int i=0;i<N;i++) {
			A[i] = sc.nextLong();
		}
		Arrays.parallelSort(A);
		for(int i=1;i<N;i++) {
			if (A[i]==A[i-1]) {
				System.out.print("NO");
				return ;
			}
		}
		System.out.print("YES");
		return ;
	}
}