n, m = map(int, input().split())
WA = []
AC = []
c = 0
S = input()

for s in S:
    if s == "W":
        WA.append(1)
    elif s == "C":
        AC.append(-1)
    elif c < m:
        c += 1
        AC.append(1)
    else:
        WA.append(-1)


def ok(S):
    tot = 0
    for s in S:
        tot += s
        if tot < 0:
            return False
    return tot == 0


if ok(WA) and ok(AC):
    print("Yes")
else:
    print("No")