import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) StringBuilder sb = new StringBuilder(); sb new StringBuilder() int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] h = new int[n]; h new int[n] n for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			h[i] = sc.nextInt();
		} {
			h[i] = sc.nextInt();
		} h[i] = sc.nextInt() h[i] h i sc.nextInt() sc.nextInt sc boolean ok = true; ok true for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		} int i = 1; int i = 1; i 1 i < n i n i++ i++ i {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		} {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		} if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			} h[i - 1] <= h[i] h[i - 1] h i - 1 i 1 h[i] h i {

			} if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			} h[i - 1] <= h[i] + 1 h[i - 1] h i - 1 i 1 h[i] + 1 h[i] h i 1 {
				h[i]++;
			} h[i]++ h[i] h i {
				ok = false;
				break;
			} ok = false ok false break; if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		} ok {
			System.out.println("Yes");
		} System.out.println("Yes") System.out.println System.out System System.out "Yes" {
			System.out.println("No");
		} System.out.println("No") System.out.println System.out System System.out "No" String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		int n = sc.nextInt();
		int[] h = new int[n];
		for (int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		boolean ok = true;
		for (int i = 1; i < n; i++) {
			if (h[i - 1] <= h[i]) {

			} else if (h[i - 1] <= h[i] + 1) {
				h[i]++;
			} else {
				ok = false;
				break;
			}
		}
		if (ok) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
}