The input consists of natural number N and M (N <= 2*10^5 and M < N).

Then you are given a permutation of numbers [1, N]
You should sort the given array, but only the following operation is allowed:
Chose a number with index from [0, M-1] and  choose a number from [M, N-1], then swap then.
What is the minimum number of operations to sort the array?

Example: Input:

5 3
1 2 3 5 4

**Steps:**
1. 1 2 5 3 4 (swap 3 and 5)
2. 1 2 4 3 5 (swap 4 and 5)
3. [1 2 3 4 5] (swap 3 and 4, now the array is sorted, total steps = 3)

Any idea on how to solve this problem?