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