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

int main() {
    int Kr, Kb;
    string S;
    cin >> Kr >> Kb >> S;

    int ans = 0;
    for (int bit_r = 0; bit_r < (1 << 10); bit_r++) {
        for (int bit_b = 0; bit_b < (1 << 10); bit_b++) {
            int now_r = 0, now_b = 0;
            string s;
            for (auto& c : S) {
                if (c == 'R') {
                    if (!(bit_r & 1 << now_r))
                        s.push_back('R');
                    now_r++;
                } else if (c == 'B') {
                    if (!(bit_b & 1 << now_b))
                        s.push_back('B');
                    now_b++;
                } else
                    s.push_back('W');
            }

            bool flag = true;
            for (int i = 0; i < 30; i++) {
                int c = s[i];
                if (c == 'R') {
                    if (i - Kr >= 0) {
                        if (s[i - Kr] == 'R')
                            flag = false;
                    }
                    if (i + Kr < 30)
                        if (s[i + Kr] == 'R')
                            flag = false;
                }
                if (c == 'B') {
                    if (i - Kb >= 0) {
                        if (s[i - Kb] == 'B')
                            flag = false;
                    }
                    if (i + Kb < 30)
                        if (s[i + Kb] == 'B')
                            flag = false;
                }
                if (!flag)
                    break;
            }
            if (flag) ans = max(ans, int(s.size()));
        }
    }
    cout << ans << endl;
}