import sequtils,strutils,math

proc matchstr(s : string,c : char, index : int): bool =
    if index < 0:
        return false
    if index > s.high:
        return false
    if s[index] == c:
        return true
    else:
        return false


var
    Kr,Kb : int
    S : string
    ans = 0
(Kr,Kb) = stdin.readline.split.map(parseInt)
S = stdin.readline

for i in 1..<(1 shl 20):
    var
        j = i
        ns = ""
        flag = true
    for s in S:
        if s == 'W':
            ns &= "W"
        else:
            if j mod 2 == 1:
                ns &= s
            j = j shr 1
    for index,s in ns:
        if s == 'W':
            continue
        elif (s == 'R' and
            (matchstr(ns,s,index + Kr) or
            matchstr(ns,s,index - Kr))):
            flag = false
            break
        elif (s == 'B' and
            (matchstr(ns,s,index + Kb) or 
            matchstr(ns,s,index - Kb))):
            flag = false
            break
    if flag:
        ans = max(ans,ns.len)
echo ans