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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			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()-1;
		
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			h[i] = sc.nextInt()-1;
		
		} {
			h[i] = sc.nextInt()-1;
		
		} h[i] = sc.nextInt()-1 h[i] h i sc.nextInt()-1 sc.nextInt() sc.nextInt sc 1 sc.close() sc.close sc int temp = -1; temp -1 1 for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		} int i = 0; int i = 0; i 0 i < n-1 i n-1 n 1 i++ i++ i {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		} {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		} if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			} h[i] - h[i+1] == 1 h[i] - h[i+1] h[i] h i h[i+1] h i+1 i 1 1 {
				h[i+1] = h[i+1] + 1;
			} h[i+1] = h[i+1] + 1 h[i+1] h i+1 i 1 h[i+1] + 1 h[i+1] h i+1 i 1 1 if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 } h[i] - h[i+1] >= 2 h[i] - h[i+1] h[i] h i h[i+1] h i+1 i 1 2 {
				temp = 0;
			break;
		 } temp = 0 temp 0 break; if(temp == -1) {
			System.out.println("Yes");
			
		} temp == -1 temp -1 1 {
			System.out.println("Yes");
			
		} System.out.println("Yes") System.out.println System.out System System.out "Yes" if(temp == 0) {
			System.out.println("No");
		} temp == 0 temp 0 {
			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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			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()-1;
		
		}
		sc.close();
		int temp = -1;
		
		for(int i = 0; i < n-1 ; i++) {
			if(h[i] - h[i+1] == 1) {
				h[i+1] = h[i+1] + 1;
			}
			if(h[i] - h[i+1] >= 2) {
				temp = 0;
			break;
		 }
		}
		if(temp == -1) {
			System.out.println("Yes");
			
		}
		if(temp == 0) {
			System.out.println("No");
		}

	}
	}
