import 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++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	}
} import java.util.*; util.* java 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++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	}
} 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++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		long[] a = new long[N];
		for(int i = 0;i < N;i++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	} 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++) {
			long A = sc.nextLong();
			a[i] += A;
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			long A = sc.nextLong();
			a[i] += A;
		} {
			long A = sc.nextLong();
			a[i] += A;
		} long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc a[i] += A a[i] a i A Arrays.parallelSort(a) Arrays.parallelSort Arrays a for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			} int j=0; int j=0; j 0 j<N-1 j N-1 N 1 j++ j++ j {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			} {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			} if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				} a[j]-a[j+1]==0 a[j]-a[j+1] a[j] a j a[j+1] a j+1 j 1 0 {
					System.out.println("NO");
					return;
				} System.out.println("NO") System.out.println System.out System System.out "NO" return; System.out.println("YES") System.out.println System.out System System.out "YES" 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++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	}
} 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++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	}
} Main
import 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++) {
			long A = sc.nextLong();
			a[i] += A;
		}
			Arrays.parallelSort(a);		
			for(int j=0;j<N-1;j++) {
				if(a[j]-a[j+1]==0) {
					System.out.println("NO");
					return;
				}
			}
			System.out.println("YES");
	}
}