import java.util.Scanner;

public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	}
}
 import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	}
} Main public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	} main {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	} try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		} {
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		} Scanner scan = new Scanner(System.in) Scanner scan = new Scanner(System.in) new Scanner(System.in) Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] X = new int[N]; X new int[N] N for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
				X[i] = sc.nextInt();
			} {
				X[i] = sc.nextInt();
			} X[i] = sc.nextInt() X[i] X i sc.nextInt() sc.nextInt sc boolean flag = true; flag true for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			} int i = N - 2 ; int i = N - 2 ; i N - 2 N 2 i >= 0 i 0 i-- i-- i {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			} {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			} if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				} X[i] > X[i + 1] X[i] X i X[i + 1] X i + 1 i 1 {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				} if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					} X[i] - X[i + 1] == 1 X[i] - X[i + 1] X[i] X i X[i + 1] X i + 1 i 1 1 X[i]-- X[i] X i {
						flag = false;
						break;
					} flag = false flag false break; System.out.println((flag)?"Yes":"No") System.out.println System.out System System.out (flag)?"Yes":"No" (flag) "Yes" "No" String[]args args public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	}
} public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			Scanner sc = new Scanner(System.in);
			int N = sc.nextInt();
			int[] X = new int[N];
			for(int i = 0; i < N; i++) {
				X[i] = sc.nextInt();
			}
			boolean flag = true;
			for(int i = N - 2 ; i >= 0; i--) {
				if(X[i] > X[i + 1]) {
					if(X[i] - X[i + 1] == 1)X[i]--;
					else{
						flag = false;
						break;
					}
				}
			}
	 
			System.out.println((flag)?"Yes":"No");
	 
		}
			
			
			
	}
}

