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");
  }
} 
     import java.util.*; util.* java 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");
  }
} 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");
  } main {
    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");
  } 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 int max = 0; 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]);
    } int i=0; int i=0; i 0 i<N i N i++ i++ i {
      H[i]=sc.nextInt();
      
      if(max - H[i] > 1){
        System.out.println("No");
        return;
      }
      
      max = Math.max(max, H[i]);
    } {
      H[i]=sc.nextInt();
      
      if(max - H[i] > 1){
        System.out.println("No");
        return;
      }
      
      max = Math.max(max, H[i]);
    } H[i]=sc.nextInt() H[i] H i sc.nextInt() sc.nextInt sc if(max - H[i] > 1){
        System.out.println("No");
        return;
      } max - H[i] > 1 max - H[i] max H[i] H i 1 {
        System.out.println("No");
        return;
      } System.out.println("No") System.out.println System.out System System.out "No" return; max = Math.max(max, H[i]) max Math.max(max, H[i]) Math.max Math max H[i] H i System.out.println("Yes") System.out.println System.out System System.out "Yes" 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];
    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");
  }
} 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");
  }
} Main
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");
  }
} 
    