Trampoline

Tutor-Man is a Korean hero who imitates superheroes such as Batman, Spider-Man, and Superman. Today he wants to imitate Spider-Man by jumping across the rooftops of tall buildings.

There are N tall buildings, numbered from 1 to N from left to right. Tutor-Man initially stands on building K. Because he is still not strong enough, he can jump only to the immediately adjacent building on the left or right, and only if that building is not taller than his current building.

To help Tutor-Man, Sanggeun installed trampolines on the rooftops of some buildings. If Tutor-Man jumps from a building with a trampoline using that trampoline, he can move to any other building regardless of height.

Find the maximum number of distinct buildings Tutor-Man can visit. He starts jumping from building K, and even if he visits the same building multiple times, that building is counted only once.

The first line contains the number of buildings N and the starting building number K. (3 ≤ N ≤ 300,000, 1 ≤ K ≤ N)

The second line contains N integers less than 10^6. These integers are the building heights in order from building 1 to building N.

The third line contains a string of length N consisting of . and T. If the i-th character is T, then a trampoline is installed on the rooftop of building i.

Print the maximum number of distinct buildings Tutor-Man can visit.