N, M = map(int, input().split())
S = input()

w, al, ar, c = [], [], [], []
for i in range(2 * N + 2 * M):
    if S[i] == 'W':
        w.append(i)
    elif S[i] == 'C':
        c.append(i)
    elif len(al) < M:
        al.append(i)
    else:
        ar.append(i)


for i in range(N):
    if w[i] > ar[i]:
        exit(print('No'))

for i in range(M):
    if c[i] < al[i]:
        exit(print('No'))


print('Yes')