import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


r,b = MI()
S = S()

X = []
for i in range(30):
    if S[i] != 'W':
        X.append(i)

ans = 10
for i in range(1<<20):
    delete = []
    for j in range(20):
        if (i>>j) & 1:
            delete.append(X[j])
    delete.append(100)
    A = ''
    index = 0
    for j in range(30):
        if j != delete[index]:
            A += S[j]
        else:
            index += 1
    l = len(A)
    for j in range(l):
        if A[j] == 'W':
            continue
        elif A[j] == 'R':
            if (0 <= j-r and A[j-r] == 'R') or (j+r < l and A[j+r] == 'R'):
                break
        else:
            if (0 <= j-b and A[j-b] == 'B') or (j+b < l and A[j+b] == 'B'):
                break
    else:
        ans = max(ans,l)

print(ans)