#include<iostream>
#include<vector>
using namespace std;
int Kr,Kb;
string s,now;
int ans;
void dfs(int id)
{
	if(now.size()+(s.size()-id)<=ans)return;
	if(id==s.size())
	{
		ans=now.size();
		return;
	}
	bool ok=false;
	if(s[id]=='W')ok=true;
	else if(s[id]=='R')
	{
		if(now.size()<Kr||now[now.size()-Kr]!='R')ok=true;
	}
	else
	{
		if(now.size()<Kb||now[now.size()-Kb]!='B')ok=true;
	}
	if(ok)
	{
		now+=s[id];
		dfs(id+1);
		now.pop_back();
	}
	dfs(id+1);
}
main()
{
	cin>>Kr>>Kb>>s;
	dfs(0);
	cout<<ans<<endl;
}