#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

bool ok(const string& s, char c, int k)
{
    for(int i=0;i<s.size();++i)
        if (s[i]==c and ((i+k<s.size() and s[i+k]==c) or (i-k>=0 and s[i-k]==c)))
            return false;
    return true;
}

int main()
{
    int r, b;
    string s;
    while (cin>>r>>b>>s) {
        int res=0;
        vector<int> x;
        for(int i=0;i<s.size();++i) if (s[i]!='W') x.push_back(i);
        for(int i=0;i<(1<<20);++i) {
            if (s.size()-__builtin_popcount(i)<=res) continue;
            string t;
            vector<int> v;
            for(int j=0;j<20;++j) if (i&(1<<j)) v.push_back(x[j]);
            for(int j=0,p=0;j<s.size();++j) {
                if (p>=v.size() or j!=v[p] )
                    t+=s[j];
                else
                    ++p;
            }
            if (ok(t, 'R', r) and ok(t, 'B', b)) res=t.size();
        }
        cout<<res<<endl;
    }
}