#include <bits/stdc++.h>
using namespace std;

#define REP(i, n) for(ll i = 0; i < (ll)(n); i++)
#define FOR(i,n,m) for (ll i=n; i < (ll)(m); i++)
#define INF 1000000007
#define pb push_back
#define MAX_N 200
#define MAX_T 10010

typedef long long ll;

int Kr,Kb;
string S;

ll gcd(ll a, ll b){
    if(b == 0) return a;
    return gcd(b, a%b);
}

ll lcm(ll a, ll b){
    return a * b / gcd(a,b);
}

bool chk(string &s){
    REP(i,s.length()){
        if(s[i]=='R'){
            if(i+Kr<s.length() && s[i+Kr]=='R') return false;
            if(i-Kr>=0 && s[i-Kr]=='R') return false;
        }
        if(s[i]=='B'){
            if(i+Kb<s.length() && s[i+Kb]=='B') return false;
            if(i-Kb>=0 && s[i-Kb]=='B') return false;
        }
    }
    return true;
}

string int2bit(int n){
    string ret="";
    REP(i,20){
        if(n>>i & 1) ret+="1";
        else ret+="0";
    }
    return ret;
}

int main(){
    cin >> Kr >> Kb >> S;
    int rcnt=0,bcnt=0;
    int b[10],a[10];
    REP(i,30){
        if(S[i]=='R'){
            a[rcnt]=i;
            rcnt++;
        }
        if(S[i]=='B'){
            b[bcnt]=i;
            bcnt++;
        }
    }
    int ans=0;
    REP(mask,1<<21){
        int use[30];
        REP(i,30){
            if(S[i]=='W') use[i]=1;
            else use[i]=0;
        }
        REP(i,10){
            if(mask>>i & 1) use[a[i]]=1;
        }
        REP(i,10){
            if(mask>>(i+10) & 1) use[b[i]]=1;
        }
        string ts="";
        REP(i,30){
            if(use[i]) ts+=S[i];
        }
        if(chk(ts)) ans=max(ans,(int)ts.length());//cout<<ts<<endl;}

    }
    
    cout << ans << endl;
    
    return 0;
}