import java.util.*;
import static java.lang.Math.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	}
} import java.util.*; util.* java import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	} main {
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	} 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 String result = "Yes"; result "Yes" for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		} {
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		} h[i] = sc.nextInt() h[i] h i sc.nextInt() sc.nextInt sc if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    } i > 0 && h[i - 1] < h[i] i > 0 i 0 h[i - 1] < h[i] h[i - 1] h i - 1 i 1 h[i] h i {
                h[i]--;		        
		    } h[i]-- h[i] h i if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    } i > 0 && h[i - 1] > h[i] i > 0 i 0 h[i - 1] > h[i] h[i - 1] h i - 1 i 1 h[i] h i {
		        result = "No";
		    } result = "No" result "No" System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	}
} Main
import java.util.*;
import static java.lang.Math.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		int n = sc.nextInt();
		int[] h = new int[n];
		
		String result = "Yes";
		
		for(int i = 0; i < n; i++){
		    h[i] = sc.nextInt();
		    if(i > 0 && h[i - 1] < h[i]){
                h[i]--;		        
		    }else if(i > 0 && h[i - 1] > h[i]){
		        result = "No";
		    }
		}
		
		// 計算

		// 出力
        System.out.println(result);
		
	}
}
