n,m=map(int,input().split())
s=input()
w=[]
a=[]
c=[]
for i,j in enumerate(s):
    if j=='W': w.append(i)
    elif j=='A': a.append(i)
    else : c.append(i)

ok=1
for i in range(m):
    ok&=(a[i]<c[i])
for i in range(n):
    ok&=(w[i]<a[i+m])

def Yes(ok):
    if ok: return "Yes"
    else: return "No"

ans=Yes(ok)
print(ans)