Climb Stairs With Minimum Moves

easy

1. You are given a number n, representing the number of stairs in a staircase.
2. You are on the 0th step and are required to climb to the top.
3. You are given n numbers, where ith element's value represents - till how far from the step you 
     could jump to in a single move.  You can of-course fewer number of steps in the move.
4. You are required to print the number of minimum moves in which you can reach the top of 
     staircase.
Note -&gt; If there is no path through the staircase print null.

Input Format

A number n .. n more elements

Output Format

A number representing the number of ways to climb the stairs from 0 to top.

Constraints

0 &lt;= n &lt;= 20
0 &lt;= n1, n2, .. &lt;= 20

Notice

Try First, Check Solution later

1. You should first read the question and watch the question video.
2. Think of a solution approach, then try and submit the question on editor tab.
3. We strongly advise you to watch the solution video for prescribed approach.

Example

Input

Output

Climb Stairs With Variable Jumps

Min Cost In Maze Traversal