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

int block[30];

int main() {
	int Kr, Kb;
	cin >> Kr >> Kb;
	string S;
	cin >> S;
	vector<int> first;
	int N = S.size();
	for (int i = 0; i < N; i++)
	{
		if (S[i] == 'R') first.push_back(1);
		else if (S[i] == 'B')first.push_back(2);
		else first.push_back(0);
	}
	int nonW = 0;
	for (int i = 0; i < N; i++)
	{
		if (first[i] != 0) nonW++;
	}

	int ans = 0;
	for (int t = 0; t < (1 << nonW); t++)
	{
		int p = 0;
		int q = 0;
		for (int i = 0; i < N; i++)
		{
			if (!first[i]) block[p++] = 0;
			else if ((t >> (q++)) % 2 == 1) block[p++] = first[i];
		}
		bool flag = true;
		for (int i = 0; i < p; i++)
		{
			if (block[i] == 1){
				if (i + Kr < p && block[i + Kr] == 1) flag = false;
			}
			else if (block[i] == 2){
				if (i + Kb < p && block[i + Kb] == 2) flag = false;
			}
		}
		if (flag){
			ans = max(ans, p);
		}
	}
	cout << ans << endl;
}