import sys, math
sys.setrecursionlimit(10**8)
sys.set_int_max_str_digits(0)
INF = 1e18
MOD = 998244353
from bisect import bisect_left, bisect_right
from collections import deque, defaultdict, Counter
from itertools import product, combinations, permutations, groupby, accumulate
from heapq import heapify, heappop, heappush
from sortedcontainers import SortedList
input = sys.stdin.readline
def I():   return input().rstrip()
def II():  return int(input().rstrip())
def IS():  return input().rstrip().split()
def MII(): return map(int, input().rstrip().split())
def LI():  return list(input().rstrip())
def TII(): return tuple(map(int, input().rstrip().split()))
def LII(): return list(map(int, input().rstrip().split()))
def LSI(): return list(map(str, input().rstrip().split()))
def GMI(): return list(map(lambda x: int(x) - 1, input().rstrip().split()))
def kiriage(a, b): return (a+b-1)//b

N, M = MII()
S = I()
W, C = [], []
A = deque()
for i, s in enumerate(S):
    if s == 'W':
        W.append(i)
    elif s == 'C':
        C.append(i)
    else:
        A.append(i)

# W 大きいものからマッチング
while W:
    pos = W.pop()
    partner = A.pop()
    if pos > partner:
        exit(print('No'))

# C 小さいものからマッチング
C.reverse()
while C:
    pos = C.pop()
    partner = A.popleft()
    if pos < partner:
        exit(print('No'))

print('Yes')