import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
} import java.util.LinkedHashMap; LinkedHashMap java.util import java.util.Map; Map 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();
		int[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				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[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				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[] 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 int pre = -1; pre -1 1 for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		} int i = 0; int i = 0; i 0 i  < n i n i++ i++ i {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		} {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		} if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			} pre <= h[i]-1 pre h[i]-1 h[i] h i 1 {
				pre = h[i]-1;
			} pre = h[i]-1 pre h[i]-1 h[i] h i 1 if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			} pre <= h[i] pre h[i] h i {
				pre = h[i];
			} pre = h[i] pre h[i] h i {
				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[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				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[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
} Main
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] h = new int[n];
		for(int i = 0; i < n; i++) {
			h[i] = sc.nextInt();
		}
		int pre = -1;
		for(int i = 0; i  < n; i++) {
			if(pre <= h[i]-1) {
				pre = h[i]-1;
			}
			else if(pre <= h[i]) {
				pre = h[i];
			}
			else {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
}