Get Number Operations (Package Sorting Passes)

You are given a permutation of 1..n. In each round, scan from left to right and process the next not-yet-processed number as soon as you reach it; several numbers can be processed in a row within one round. Find how many rounds are needed to process all numbers.

输入格式

The first line contains n (1..1000000), and the second line contains a permutation of 1..n.

输出格式

Output a single integer answer.

样例 1

输入：

5
5 3 4 1 2

输出：

3

样例 2

输入：

1
1

输出：

1

样例 3

输入：

3
3 2 1

输出：

3

样例说明

Example 1: the first round processes 1, 2; the second 3, 4; the third 5, so the answer is 3. Example 2: a single scan finishes. Example 3: each round can process only one number, so the answer is 3.