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