I=input
N,M=map(int,I().split())
S=I()
a=c=w=b=0
for i in range((N+M)*2):
	if S[i]<"C":a+=1
	elif S[i]>"C":
		w+=1
		b+=M+w<a
	else:
		c+=1
		b+=a<c
print("No"if b else"Yes")