import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int kr = sc.nextInt();
        int kb = sc.nextInt();
        char[] inputs = sc.next().toCharArray();
        int[] idxes = new int[inputs.length];
        int counter = 0;
        for (int i = 0; i < inputs.length; i++) {
            if (inputs[i] == 'W') {
                idxes[i] = -1;
            } else {
                idxes[i] = counter++;
            }
        }
        int ans = 0;
        char[] tmp = new char[inputs.length];
        for (int i = 0; i < (1 << counter); i++) {
            int k = 0;
            boolean enable = true;
            for (int j = 0; j < inputs.length; j++) {
                if (idxes[j] == -1) {
                    tmp[k++] = 'W';
                } else {
                    if ((i & (1 << idxes[j])) == 0) {
                        continue;
                    }
                    if (inputs[j] == 'R') {
                        if (k - kr >= 0 && tmp[k - kr] == 'R') {
                            enable = false;
                            break;
                        }
                        tmp[k++] = 'R';
                    } else {
                        if (k - kb >= 0 && tmp[k - kb] == 'B') {
                            enable = false;
                            break;
                        }
                        tmp[k++] = 'B';
                    }
                }
            }
            if (enable) {
                ans = Math.max(ans, k);
            }
        }
        System.out.println(ans);
    }
}

class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}