#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000

int main(){
	
	int Kr,Kb;
	cin>>Kr>>Kb;
	
	string s;
	cin>>s;
	
	vector<int> inds;
	rep(i,s.size()){
		if(s[i]!='W')inds.push_back(i);
	}
	int ans = 0;
	rep(i,1<<20){
		vector<bool> f(30,true);
		rep(j,20){
			if((i>>j)&1)f[inds[j]] = false;
		}
		string temp = "";
		rep(j,30){
			if(f[j])temp += s[j];
		}
		bool F = true;
		rep(j,temp.size()){
			if(temp[j]=='B'&&j-Kb>=0){
				if(temp[j-Kb]=='B')F = false;
			}
			if(temp[j]=='R'&&j-Kr>=0){
				if(temp[j-Kr]=='R')F = false;
			}
		}
		if(F)ans = max(ans,(int)temp.size());
	}
	
	cout<<ans<<endl;
	
	return 0;
}