#include<cstdio>
#define int long long
using namespace std;
const int N=2e5+10;
int a[N]; char s[N]; bool l[N],r[N];
void file() { freopen("P10188_12.in","r",stdin); }
signed main() {
  file();
  int n,m,ans=0; scanf("%lld %lld %s",&n,&m,s+1);
  for(int i=1;i<=n;i++) scanf("%lld",&a[i]),ans+=a[i];
  for(int i=1;i<=n;i++)
    if(s[i]=='R'&&s[i%n+1]=='L') l[i]=r[i%n+1]=true;
  for(int i=1;i<=n;i++) {
  	int sum=0;
  	if(l[i])
  	  for(int j=i-1;s[j]=='R';j--) {
  	    if(!j) j=n;
  	    sum+=a[j];
	  }
	if(r[i])
	  for(int j=i+1;s[j]=='L';j++) {
  	    if(j>n) j=1;
  	    sum+=a[j];
	  }
	if(sum<m) ans-=sum;
	else ans-=m;
  }
  printf("%lld",ans);
  return 0;
}