import 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 = 1;

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


        System.out.println("Yes");
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz