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

w_sum = [0] * (2 * (n + m) + 1)
a_sum = [0] * (2 * (n + m) + 1)
c_sum = [0] * (2 * (n + m) + 1)

for i in range(2 * (n + m)):
    w_sum[i + 1] = w_sum[i]
    a_sum[i + 1] = a_sum[i]
    c_sum[i + 1] = c_sum[i]
    if s[i] == 'W':
        w_sum[i + 1] += 1
    elif s[i] == 'A':
        a_sum[i + 1] += 1
    else:
        c_sum[i + 1] += 1
    if c_sum[i + 1] > a_sum[i + 1] or w_sum[i + 1] < a_sum[i + 1] - m:
        print('No')
        exit()
print('Yes')