import java.util.Scanner;
class Main{


	static char[][] map;
	static final int MOD = 1000000007;


	static long[][] c;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力

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





	}



	static int gcd(int a,int b){				//最大公約数を返す
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	}
	static long gcd(long a,long b){
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	}



	static long lcm (long a, long b) {
		long g = gcd(a,b);
		return a/g*b;
	}




}



class Pair implements Comparable{
	int from;
	int end;
	@Override
	public int compareTo(Object other) {
		Pair otherpair = (Pair)other;

		return   end- otherpair.end;
	}








}



 import java.util.Scanner; Scanner java.util class Main{


	static char[][] map;
	static final int MOD = 1000000007;


	static long[][] c;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力

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





	}



	static int gcd(int a,int b){				//最大公約数を返す
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	}
	static long gcd(long a,long b){
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	}



	static long lcm (long a, long b) {
		long g = gcd(a,b);
		return a/g*b;
	}




} Main static char[][] map; map static final int MOD = 1000000007; MOD 1000000007 static long[][] c; c public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力

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





	} main {
		Scanner sc = new Scanner(System.in);			//文字の入力

		int n = sc.nextInt();
		int[] h = new int[n];
		for(int i = 0;i < n;i++){
			h[i] = sc.nextInt();
		}
		for(int i = n-1;i >= 1;i--){
			if(h[i-1] > h[i]){
				h[i-1]--;
				if(h[i-1] > h[i]){
					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 for(int i = n-1;i >= 1;i--){
			if(h[i-1] > h[i]){
				h[i-1]--;
				if(h[i-1] > h[i]){
					System.out.println("No");
					return;
				}
			}
		} int i = n-1; int i = n-1; i n-1 n 1 i >= 1 i 1 i-- i-- i {
			if(h[i-1] > h[i]){
				h[i-1]--;
				if(h[i-1] > h[i]){
					System.out.println("No");
					return;
				}
			}
		} {
			if(h[i-1] > h[i]){
				h[i-1]--;
				if(h[i-1] > h[i]){
					System.out.println("No");
					return;
				}
			}
		} if(h[i-1] > h[i]){
				h[i-1]--;
				if(h[i-1] > h[i]){
					System.out.println("No");
					return;
				}
			} h[i-1] > h[i] h[i-1] h i-1 i 1 h[i] h i {
				h[i-1]--;
				if(h[i-1] > h[i]){
					System.out.println("No");
					return;
				}
			} h[i-1]-- h[i-1] h i-1 i 1 if(h[i-1] > h[i]){
					System.out.println("No");
					return;
				} h[i-1] > h[i] h[i-1] h i-1 i 1 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 static int gcd(int a,int b){				//最大公約数を返す
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	} gcd {				//最大公約数を返す
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	} if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		} b == 0 b 0 {
			return a;
		} return a; a {
			return gcd(b, a%b);
		} return gcd(b, a%b); gcd(b, a%b) gcd b a%b a b int a a int b b static long gcd(long a,long b){
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	} gcd {
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	} if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		} b == 0 b 0 {
			return a;
		} return a; a {
			return gcd(b, a%b);
		} return gcd(b, a%b); gcd(b, a%b) gcd b a%b a b long a a long b b static long lcm (long a, long b) {
		long g = gcd(a,b);
		return a/g*b;
	} lcm {
		long g = gcd(a,b);
		return a/g*b;
	} long g = gcd(a,b); g gcd(a,b) gcd a b return a/g*b; a/g*b a/g a g b long a a long b b class Pair implements Comparable{
	int from;
	int end;
	@Override
	public int compareTo(Object other) {
		Pair otherpair = (Pair)other;

		return   end- otherpair.end;
	}








} Pair int from; from int end; end @Override
	public int compareTo(Object other) {
		Pair otherpair = (Pair)other;

		return   end- otherpair.end;
	} compareTo {
		Pair otherpair = (Pair)other;

		return   end- otherpair.end;
	} Pair otherpair = (Pair)other; otherpair (Pair)other return   end- otherpair.end; end- otherpair.end end otherpair.end otherpair otherpair.end Object other other Comparable
import java.util.Scanner;
class Main{


	static char[][] map;
	static final int MOD = 1000000007;


	static long[][] c;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);			//文字の入力

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





	}



	static int gcd(int a,int b){				//最大公約数を返す
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	}
	static long gcd(long a,long b){
		if(b == 0){
			return a;
		}else{
			return gcd(b, a%b);
		}
	}



	static long lcm (long a, long b) {
		long g = gcd(a,b);
		return a/g*b;
	}




}



class Pair implements Comparable{
	int from;
	int end;
	@Override
	public int compareTo(Object other) {
		Pair otherpair = (Pair)other;

		return   end- otherpair.end;
	}








}




