#include <algorithm>
#include <iostream>
#include <string>

using namespace std;

int Kr, Kb;
string S;

bool check(const string& str) {
	for (int i = 0; i < str.length(); i++) {
		if (str[i] == 'R' && i + Kr < str.length() && str[i + Kr] == 'R') {
			return false;
		}
		if (str[i] == 'B' && i + Kb < str.length() && str[i + Kb] == 'B') {
			return false;
		}
	}
	return true;
}

int main() {
	cin >> Kr >> Kb >> S;
	int s = 0;
	for (int i = 0; i < S.length(); i++) {
		if (S[i] != 'W') {
			s |= (1 << i);
		}
	}
	int res = 0;
	int comb = s;
	do {
		string str;
		for (int i = 0; i < S.length(); i++) {
			if (((comb >> i) & 1) == 0) {
				str += S[i];
			}
		}
		if (check(str)) {
			res = max(res, (int)str.length());
		}
		comb = (comb - 1) & s;
	} while (comb != s);
	cout << res << endl;
	return 0;
}