#include <iostream>
#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <sstream>
#include <algorithm>
#include <functional>
#include <limits.h>
#include <bitset>

#include <tuple>
#include <unordered_map>

#define mp       make_pair
#define mt       make_tuple
#define pb       push_back
#define rep(i,n) for(int i=0;i<(n);i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};

int Kr,Kb;
string S;
int N;
vector<int> indexs;
bool used[30];
int main(){
  cin >> Kr >> Kb;
  cin >> S;
  N = S.size();
  for (int i = 0; i < N; i++){
    if (S[i] != 'W'){
      indexs.push_back(i);
    }
  }
  int ans = 0;
  for (int bit = 0; bit < (1 << indexs.size()); bit++){
    memset(used, false, sizeof(used));
    
    for (int i = 0; i < N; i++){
      if (S[i] == 'W'){
	used[i] = true;
      }
    }
    for (int i = 0; i < indexs.size(); i++){
      if (bit >> i & 1){
	used[indexs[i]] = true;
      }
    }
    string tmp = "";
    for (int i = 0; i < N; i++){
      if (used[i]){
	tmp += S[i];
      }
    }
    if (tmp.size() <= ans)continue;
    bool ok = true;
    for (int i = 0; i < tmp.size(); i++){
      if (tmp[i] == 'R'){
	if (i - Kr >= 0){
	  ok &= tmp[i - Kr] == 'R' ? false : true;
	}
	if (i + Kr < tmp.size()){
	  ok &= tmp[i + Kr] == 'R' ? false : true;	  
	}
      }
      if (tmp[i] == 'B'){
	if (i - Kb >= 0){
	  ok &= tmp[i - Kb] == 'B' ? false : true;
	}
	if (i + Kb < tmp.size()){
	  ok &= tmp[i + Kb] == 'B' ? false : true;	  
	}
      }
    }
    
    if (ok){
      ans = max(ans, (int)tmp.size());
    }
  }
  cout << ans << endl;
}