import java.util.Scanner;


public class Main_yukicoder38 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int kr = sc.nextInt();
        int kb = sc.nextInt();
        char[] s = sc.next().toCharArray();

        int max = 0;
        for (int mask = 0; mask < 0x1 << 20; mask++) {
            int ir = 0;
            int ib = 0;
        	StringBuilder tmp = new StringBuilder();
            for (int i = 0; i < s.length; i++) {
            	if (s[i] == 'R') {
            		if ((mask & 0x1 << ir++) != 0) {
            			continue;
            		}
            	} else if (s[i] == 'B') {
            		if ((mask & 0x1 << 10 + ib++) != 0) {
            			continue;
            		}
            	}

            	tmp.append(s[i]);
            }

        	if (isOK(tmp, kr, kb)) {
        		max = Math.max(max, 30 - Integer.bitCount(mask));
        	}
        }

        System.out.println(max);

        sc.close();
    }

	private static boolean isOK(StringBuilder s, int kr, int kb) {
		int n = s.length();
		for (int i = 0; i < n; i++) {
			if (s.charAt(i) == 'R') {
				if (i - kr >= 0 && s.charAt(i - kr) == 'R') {
					return false;
				}
				if (i + kr < n && s.charAt(i + kr) == 'R') {
					return false;
				}
			} else if (s.charAt(i) == 'B') {
				if (i - kb >= 0 && s.charAt(i - kb) == 'B') {
					return false;
				}
				if (i + kb < n && s.charAt(i + kb) == 'B') {
					return false;
				}
			}
		}

		return true;
	}
}