import java.util.Scanner;

public class Yuki038 {
    public static void main(String[] args) {
        Yuki038 hoge = new Yuki038();
    }

    Yuki038() {
        Scanner scanner = new Scanner(System.in);
        int kr = scanner.nextInt();
        int kb = scanner.nextInt();
        String s = scanner.next();
        int ans = 0;
        int N = s.length();
        int mask = 0;
        for (int i = 0; i < N; i++) {
            if (s.charAt(i) == 'W') {
                mask |= 1 << i;
            }
        }

        for (int i = mask; i < (1 << N); i = (i + 1) | mask) {
            String t = "";
            for (int j = 0; j < N; j++) {
                if (s.charAt(j) == 'W' || (((1 << j) & i) > 0)) {
                    t += s.charAt(j);
                }
            }
            boolean hit = false;

            for (int j = 0; j < t.length(); j++) {
                if (t.charAt(j) == 'W') {
                    continue;
                }

                for (int[] c : new int[][]{{'R', kr}, {'B', kb}}) {
                    if (s.charAt(j) == c[0]) {
                        if (j >= c[1]) {
                            if (t.charAt(j - c[1]) == c[0]) {
                                hit = true;
                                break;
                            }
                        }
                        if (j + c[1] < t.length()) {
                            if (t.charAt(j + c[1]) == c[0]) {
                                hit = true;
                                break;
                            }
                        }
                    }
                }
                if (hit) {
                    break;
                }
            }
            if (!hit) {
                ans = Math.max(ans, t.length());
            }

        }
        System.out.println(ans);

    }

}