A1441.[COCI-2011_2012-contest1]#5 SORT

Consider the following sorting algorithm:
reverse-sort(sequence a)
while (a is not in nondecreasing order)
partition a into the minimum number of slopes for every slope with length greater than one reverse(slope)
A slope is defined as a decreasing consecutive subsequence of a. The reverse procedure will reverse the order of the elements in a slope.
You are given a permutation of the first N natural numbers whose slopes all have even length when partitioned for the first time. Determine the total number of times reverse is called to reverse-sort the given permutation.

The first line of input contains the positive integer N (2 ≤ N ≤ 100 000).
The second line of input contains a permutation of the first N natural numbers that needs to be sorted.

The only line of output must contain the number of times that reverse is called.