#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000009
#define INF 1000000000
#define LLINF 2000000000000000000LL
#define PI 3.1415926536

#define SIZE 101

int kr,kb,ans;
string S;
set<string> memo;

int dfs(string s){
    bool f =true;
    string ch;
    int ret = 0;
    
    if(s.size() <= ans) return 0;
    if(memo.find(s)!=memo.end()) return 0;
    memo.insert(s);
    
    for(int i=0;i<=s.size();i++){
        if(s[i]=='R'){
            if(0<=i-kr && s[i-kr]=='R') f = false;
            if(i+kr<s.size() && s[i+kr]=='R') f = false;
        }
        if(s[i]=='B'){
            if(0<=i-kb && s[i-kb]=='B') f = false;
            if(i+kb<s.size() && s[i+kb]=='B') f = false;
        }
    }
    
    if(f){
        ans = s.size();
        return (int)s.size();
    }
    
    for(int i=0;i<s.size();i++){
        ch = s;
        ch.erase(ch.begin()+i);
        ret = max(dfs(ch),ret);
    }
    
    return ret;
}

int main(){
    
    cin >> kr >> kb >> S;
    
    cout << dfs(S) << endl;
    
    return 0;
}