import 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();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				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();
		int A[] = new int[N];
		for(int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				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();
		int A[] = new int[N];
		for(int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	} 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();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				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 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 Arrays.sort(A) Arrays.sort Arrays A for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				System.out.println("NO");
				return;
			}
		} 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]) {
				System.out.println("NO");
				return;
			}
		} {
			if(A[i] == A[i + 1]) {
				System.out.println("NO");
				return;
			}
		} if(A[i] == A[i + 1]) {
				System.out.println("NO");
				return;
			} A[i] == A[i + 1] A[i] A i A[i + 1] A i + 1 i 1 {
				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();
		int A[] = new int[N];
		for(int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				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();
		int A[] = new int[N];
		for(int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				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();
		int A[] = new int[N];
		for(int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.sort(A);
		for(int i = 0; i < N - 1; i++) {
			if(A[i] == A[i + 1]) {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
}
