#include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

bool is_ok (string s, char c, int K ){
	int n = s.length();
	rep (i, n ){
		if (s[i] == c ){
			if ((i - K >= 0 && s[i-K] == c )
			|| (i + K < n && s[i+K] == c ) ) return false;
		} // end if
	} // end rep

	return true;
}

int table[32];	// R, B の位置

int main()
{
	memset (table, -1, sizeof (table ) );
	ios_base::sync_with_stdio(0);
	int Kr, Kb; cin >> Kr >> Kb;
	string S; cin >> S;

	int j = 0;
	rep (i, S.length() ) if (S[i] != 'W' ) table[i] = j, j++;

	int res = 0;
	rep (i, 1<<20 ){
		string T; T = "";
		rep (j, S.length() ) {
			if (S[j] == 'W' ) T += S[j];
			else
			if (i & (1<<table[j] ) ) T += S[j];
		} // end rep
	
		bool okR = is_ok (T, 'R', Kr );
		bool okB = is_ok (T, 'B', Kb );

		if (okR && okB ){
			int curr = __builtin_popcount(i );
			if (res < curr + 10 ){
				res = curr + 10;
//				cerr << T << endl;
			} // end if	
		} // end if
	} // end rep

	cout << res << endl;

	return 0;
}