There are N bulbs, numbered from 1 to N, arranged in a row. Initially, all the bulbs are turned off. At moment K (for K from 0 to N - 1), we turn on the A[K]-th bulb. A bulb shines if it is on and all the previous bulbs are turned on too.

Return the number of moments for which every turned on bulb shines.

Example 1:

Input: A = [2, 1, 3, 5, 4]

Output: 3

Example 2:

Input: A = [2, 3, 4, 1, 5]

Output: 2

Example 3:

Input: A = [5, 4, 3, 2, 1]

Output: 1

• N is an integer within the range [1..100,000]
• the elements of A are all distinct
• each element of array A is an integer within the range [1..N]

Does anybody have a better description for this problem?