#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = (ll)(1e+9) + 7;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
typedef pair<ld, ld> LDP;
int a, b;
bool valid(string s) {
	int len = s.length();
	rep(i, len - a + 1) {
		if (s[i] == 'R'&&s[i + a] == 'R')return false;
	}
	rep(i, len - b + 1) {
		if (s[i] == 'B'&&s[i + b] == 'B')return false;
	}
	return true;
}
int main() {
	cin >> a >> b; string s; cin >> s;
	int out = 0;
	rep(i, (1 << 20)) {
		vector<int> v;
		rep(j, 20) {
			if (i&(1 << j)) {
				v.push_back(j);
			}
		}
		int c = 0;
		string t;
		rep(j, 30) {
			if (s[j] == 'W') {
				t.push_back(s[j]);
			}
			else {
				if (count(v.begin(), v.end(), c)) {
					t.push_back(s[j]);
				}
				c++;
			}
		}
		if (valid(t)) {
			out = max(out, (int)t.length());
		}
	}
	cout << out << endl;
	return 0;
}