#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef pair< int, int > pii;
typedef vector< pii > vp;
typedef vector< double > vd;
typedef vector< vd > vvd;
typedef vector< string > vs;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

int Kr, Kb;
string S;

void init(){
  cin >> Kr >> Kb;
  cin >> S;
}

vi pos;

void preprocess(){
  for( int i = 0; i < 30; ++i )
    if( S[ i ] != 'W' )
      pos.emplace_back( i );
  int ans = 0;
  for( int i = 0; i < 1 << 20; ++i ){
    vi del( 30 );
    for( int j = 0; j < 20; ++j )
      if( i & 1 << j )
        del[ pos[ j ] ] = 1;
    string t;
    for( int j = 0; j < 30; ++j )
      if( not del[ j ] )
        t += S[ j ];
    int ng = 0;
    for( int j = 0; j < t.size(); ++j ){
      if( t[ j ] == 'R' ){
        ng |= j - Kr >= 0 and t[ j - Kr ] == 'R';
        ng |= j + Kr < t.size() and t[ j + Kr ] == 'R';
      }
      if( t[ j ] == 'B' ){
        ng |= j - Kb >= 0 and t[ j - Kb ] == 'B';
        ng |= j + Kb < t.size() and t[ j + Kb ] == 'B';
      }
    }
    if( not ng )
      upmax( ans, t.size() );
  }
  cout << ans << endl;
}

void solve(){

}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}