using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;
using System.IO;

class Program
{
    static void Main()
    {
        new Magatro().Solve();
    }
}

class Magatro
{
    private int Kr, Kb;
    private string S;
    private int ans = 0;
    private const int Length = 30;
    private bool[] Use = new bool[Length];

    private void Scan()
    {
        var line = Console.ReadLine().Split(' ');
        Kr = int.Parse(line[0]);
        Kb = int.Parse(line[1]);
        S = Console.ReadLine();
    }

    private void DFS(int n, int l)
    {
        if (n == Length)
        {
            ans = Math.Max(ans, l);
            return;
        }
        if (S[n] == 'W')
        {
            Use[n] = true;
            DFS(n + 1, l + 1);
        }
        else
        {
            DFS(n + 1, l);
            int cnt = 0;
            Use[n] = true;
            if (S[n] == 'R')
            {
                for (int i = n - 1; i >= 0; i--)
                {
                    if (Use[i]) cnt++;
                    if (cnt == Kr && S[i] == 'R')
                    {
                        return;
                    }
                }
            }
            else if (S[n] == 'B')
            {
                for (int i = n - 1; i >= 0; i--)
                {
                    if (Use[i]) cnt++;
                    if (cnt == Kb && S[i] == 'B')
                    {
                        return;
                    }
                }
            }
            DFS(n + 1, l + 1);
            Use[n] = false;
        }
    }

    public void Solve()
    {
        Scan();
        DFS(0, 0);
        Console.WriteLine(ans);
    }
}