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

W = []
A = []
C = []
for i, s in enumerate(S):
    if s == "W":
        W.append(i)
    elif s == "A":
        A.append(i)
    else:
        C.append(i)

L, R = A[:M], A[M:]
print("Yes" if all(L[i] < C[i] for i in range(M)) and all(W[i] < R[i] for i in range(N)) else "No")