#include <iostream>
#include <deque>
#include <functional>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
using namespace std;
template <class T> void setmax(T & a, T const & b) { if (a < b) a = b; }
int main() {
    int kr, kb; string s; cin >> kr >> kb >> s;
    deque<char> stk;
    int ans = 0;
    function<int (int)> go = [&](int i) {
        if (stk.size() + s.length() - i <= ans) {
            return 0;
        }
        int acc = 0;
        if (i == s.length()) {
            setmax<int>(acc, stk.size());
        } else {
            if (s[i] == 'R') {
                if (kr-1 >= stk.size() or stk[kr-1] != 'R') {
                    stk.push_front('R');
                    setmax(acc, go(i+1));
                    stk.pop_front();
                }
                setmax(acc, go(i+1));
            } else if (s[i] == 'B') {
                if (kb-1 >= stk.size() or stk[kb-1] != 'B') {
                    stk.push_front('B');
                    setmax(acc, go(i+1));
                    stk.pop_front();
                }
                setmax(acc, go(i+1));
            } else {
                stk.push_front('W');
                setmax(acc, go(i+1));
                stk.pop_front();
            }
        }
        setmax(ans, acc);
        return acc;
    };
    go(0);
    cout << ans << endl;
    return 0;
}