#include<iostream>
#include<string>
#include<map>

using namespace std;

int main(){
	int kr,kb;
	cin >> kr >> kb;
	
	string s;
	cin >> s;
	
	map<int,int> mp;
	
	int ind = 0;
	for(int i = 0;i < s.size();i++){
		if(s[i] != 'W'){
			mp[i] = ind;
			ind++;
		}
	}
	
	int ans = 0;
	for(int i = ((1 << 20) - 1);i >= 0;i--){
		int tn = 0;
		string tests = "";
		for(int j = 0;j < s.size();j++){
			if(s[j] == 'W'){
				tests += s.substr(j,1);
			}else{
				if((i >> mp[j]) % 2 == 1){
					tests += s.substr(j,1);
					tn++;
				}
			}
		}
		
		bool ok = true;
		for(int j = 0;j < tests.size();j++){
			if(tests[j] == 'B'){
				if(j >= kb){
					if(tests[j - kb] == 'B' || tests[j + kb] == 'B'){
						ok = false;
						break;
					}
				}else{
					if(tests[j + kb] == 'B'){
						ok = false;
						break;
					}
				}
			}else if(tests[j] == 'R'){
				if(j >= kr){
					if(tests[j - kr] == 'R' || tests[j + kr] == 'R'){
						ok = false;
						break;
					}
				}else{
					if(tests[j + kr] == 'R'){
						ok = false;
						break;
					}
				}
			}
		}
		
		if(ok){
			ans = max(ans,tn);
		}
	}
	
	cout << (ans + 10) << endl;
	
	return 0;
}