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

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);

	boolean bl = true;
	int check = A[0];
	for (int i = 1; i < N; i++) {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	}

	if (bl)
	    System.out.println("YES");
	else
	    System.out.println("NO");
    }
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util 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);

	boolean bl = true;
	int check = A[0];
	for (int i = 1; i < N; i++) {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	}

	if (bl)
	    System.out.println("YES");
	else
	    System.out.println("NO");
    }
} 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);

	boolean bl = true;
	int check = A[0];
	for (int i = 1; i < N; i++) {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	}

	if (bl)
	    System.out.println("YES");
	else
	    System.out.println("NO");
    } 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);

	boolean bl = true;
	int check = A[0];
	for (int i = 1; i < N; i++) {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	}

	if (bl)
	    System.out.println("YES");
	else
	    System.out.println("NO");
    } 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] A i sc.nextInt() sc.nextInt sc Arrays.sort(A) Arrays.sort Arrays A boolean bl = true; bl true int check = A[0]; check A[0] A 0 for (int i = 1; i < N; i++) {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	} int i = 1; int i = 1; i 1 i < N i N i++ i++ i {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	} {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	} if (check == A[i]) {
		bl = false;
		break;
	    } check == A[i] check A[i] A i {
		bl = false;
		break;
	    } bl = false bl false break; check = A[i] check A[i] A i if (bl)
	    System.out.println("YES");
	else
	    System.out.println("NO"); bl System.out.println("YES") System.out.println System.out System System.out "YES" System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args
import java.util.Arrays;
import java.util.Scanner;

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);

	boolean bl = true;
	int check = A[0];
	for (int i = 1; i < N; i++) {
	    if (check == A[i]) {
		bl = false;
		break;
	    }

	    check = A[i];
	}

	if (bl)
	    System.out.println("YES");
	else
	    System.out.println("NO");
    }
}