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 2 5 3 4 (swap 3 and 5) - 1 2 4 3 5 (swap 4 and 5) - [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?