#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i) = 0 ; (i) < (int)(n) ; (i)++)
#define REP(i,a,b) for(int (i) = a ; (int)(i) <= (int)(b) ; (i)++)
#define all(n) (n).begin(),(n).end()
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef pair<long long,long long> Pii;
typedef vector<Pii> VPii;


int main(){
	int Kr,Kb;
	string S;
	cin >> Kr >> Kb;
	cin >> S;
	Vi p;
	int ans = 0;
	for(int i = 0 ; i < S.size() ; i++) if( S[i] != 'W' ) p.push_back(i);
	for(int i = 0 ; i < (1<<p.size()) ; i++){
		string T = S;
		for(int j = 0 ; j < p.size() ; j++){
			if( i >> j & 1 ) T[p[j]] = '#';
		}
		T.erase(remove(T.begin(),T.end(),'#'),T.end());
		int ok = 1;
		for(int j = 0 ; j < T.size() ; j++){
			if( j - Kr >= 0 && T[j-Kr] == 'R' && T[j] == 'R' ) ok = 0; 
			if( j - Kb >= 0 && T[j-Kb] == 'B' && T[j] == 'B' ) ok = 0; 
			if( j + Kr < T.size() && T[j+Kr] == 'R' && T[j] == 'R' ) ok = 0; 
			if( j + Kb < T.size() && T[j+Kb] == 'B' && T[j] == 'B' ) ok = 0; 
		}
		if(ok)ans = max(ans,(int)T.size());
	}
	cout << ans << endl;
}