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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
} 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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				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 int max_h = 0; max_h 0 for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			}
		} int i=0; int i=0; i 0 i<N i N i++ i++ i {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			}
		} {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			}
		} H[i] = sc.nextInt() H[i] H i sc.nextInt() sc.nextInt sc if(H[i] > max_h) {
				max_h = H[i];
			} H[i] > max_h H[i] H i max_h {
				max_h = H[i];
			} max_h = H[i] max_h H[i] H i if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			} max_h - H[i] > 1 max_h - H[i] max_h H[i] H i 1 {
				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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
} 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];
		int max_h = 0;
		for(int i=0;i<N;i++) {
			H[i] = sc.nextInt();

			if(H[i] > max_h) {
				max_h = H[i];
			}

			if(max_h - H[i] > 1) {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
}
