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

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

#define mygc(c) (c)=getchar_unlocked()
#define mypc(c) putchar_unlocked(c)

void reader(int *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
void reader(int *x, int *y){reader(x);reader(y);}
int reader(char c[]){int i,s=0;for(;;){mygc(i);if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF) break;}c[s++]=i;for(;;){mygc(i);if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF) break;c[s++]=i;}c[s]='\0';return s;}
void writer(int x, char c){int s=0,m=0;char f[10];if(x<0)m=1,x=-x;while(x)f[s++]=x%10,x/=10;if(!s)f[s++]=0;if(m)mypc('-');while(s--)mypc(f[s]+'0');mypc(c);}

int res = 100;
int N, R, B; char S[1000];

void solve(int depth, int deled, char now[], int len){
  int ok;
  
  if(deled >= res) return;
  if(depth==N) res = deled;

  ok = 1;
  now[len] = S[depth];
  if(now[len]=='R' && len-R>=0 && now[len-R]=='R') ok = 0;
  if(now[len]=='B' && len-B>=0 && now[len-B]=='B') ok = 0;

  if(ok) solve(depth+1, deled, now, len+1);
  solve(depth+1, deled+1, now, len);
}

int main(){
  int i, j, k;
  char now[100];

  reader(&R,&B);
  N=reader(S);
  solve(0,0,now,0);

  writer(N-res,'\n');

  return 0;
}