import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int p = 0;
    String ans = "Yes";
    for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    }
    System.out.println(ans);
  }
} 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 p = 0;
    String ans = "Yes";
    for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    }
    System.out.println(ans);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int p = 0;
    String ans = "Yes";
    for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    }
    System.out.println(ans);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int p = 0;
    String ans = "Yes";
    for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    }
    System.out.println(ans);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int p = 0; p 0 String ans = "Yes"; ans "Yes" for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    } {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    } int h = sc.nextInt(); h sc.nextInt() sc.nextInt sc if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      } h > p h p {
        h--;
        p = h;
      } h-- h p = h p h if(h == p) {
      
      } else {
        ans = "No";
        break;
      } h == p h p {
      
      } {
        ans = "No";
        break;
      } ans = "No" ans "No" break; System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int p = 0;
    String ans = "Yes";
    for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    }
    System.out.println(ans);
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int p = 0;
    String ans = "Yes";
    for(int i = 0; i < n; i++) {
      int h = sc.nextInt();
      if(h > p) {
        h--;
        p = h;
      } else if(h == p) {
      
      } else {
        ans = "No";
        break;
      }
    }
    System.out.println(ans);
  }
} Main
import java.util.*;

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