#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int r, b;
  cin >> r >> b;
  string s;
  cin >> s;

  int sub = 0;
  for (int i = 0; i < s.length(); i++) {
    if (s[i] != 'W')
      sub |= 1 << i;
  }

  int ret = 0;
  int mask = sub;
  do {
    string t;
    for (int i = 0; i < s.length(); i++) {
      if (s[i] == 'W') t += 'W';
      else if (mask & 1 << i) t += s[i];
    }

    bool ck = true;
    for (int i = 0; i < t.length(); i++) {
      if (t[i] == 'R') {
        if (i-r >= 0 && t[i-r] == 'R') {
          ck = false;
          break;
        }
      } else if (t[i] == 'B') {
        if (i-b >= 0 && t[i-b] == 'B') {
          ck = false;
          break;
        }
      }
    }
    if (ck) {
      int tmp = __builtin_popcountll(mask);
      ret = max(ret, tmp);
    }
    --mask &= sub;
  } while (mask != sub);

  ret += count(s.begin(), s.end(), 'W');
  cout << ret << endl;
  
  return 0;
}