n, k = map(int, input().split())
s = input()

# start with all kids making it to the other side
cnt = k

# current state of the bridge, initially all plates are unknown
state = ['U'] * n

# first player always chooses left at first step
state[0] = 'L'

# simulate the game for all players
for i in range(1, k):
    # copy the current state
    prev_state = state.copy()

    # follow the correct choices as far as they are known
    for j in range(n):
        if s[j] == prev_state[j]:
            state[j] = prev_state[j]
        else:
            state[j] = 'U'
            break

    # apply the switching strategy
    for j in range(n):
        if state[j] == 'U':
            if prev_state[j] == 'L':
                state[j] = 'R'
            else:
                state[j] = 'L'

    # check if the player falls at the last step or all plates are fake
    if state[-1] != s[-1] or all(p == 'R' for p in s):
        cnt -= 1

print(cnt)