I=input
N,M=map(int,I().split())
L=(N+M)*2
S,D,R=I(),[1]*L,range(L)
C="C"
j=L-1
for i in R[::-1]:
	if S[i]>C:
		D[j]=0
		while i<j and S[j]<C:j-=1
		if i<j:j-=1
		else:j=-1
a=0
for i in R:
	if S[i]<C:a+=D[i]
	elif S[i]==C:a-=1
	if a<0:break
print("No"if a<0 or j<0 else"Yes")