#include<cstdio>
#include<algorithm>
using namespace std;
int n,b[100005];
int lh,rh,lg,rg;
int a1,b1,ans;
bool a[100005];
int fh[100005],fg[100005];
char ch[100005];
int main()
{
	freopen("leaders.in","r",stdin);
	freopen("leaders.out","w",stdout);
	scanf("%d",&n);
	scanf("%s",&ch);
	for(int i=1;i<=n;i++)
	{
		a[i]=ch[i-1]=='G';
		if(a[i]&&!lg) lg=i;
		if(!a[i]&&!lh) lh=i;
		if(a[i]) rg=i;
		else rh=i;
	}
	for(int i=1;i<=n;i++)
	{
		scanf("%d",b+i);
		if(a[i]&&i<=lg&&b[i]>=rg) a1++,fg[i]=1;
		if(!a[i]&&i<=lh&&b[i]>=rh) b1++,fh[i]=1;
	}
	ans=a1*b1;
	for(int i=1;i<=lh||i<=lg;i++) 
		if(a[i]&&!fg[i]||!a[i]&&!fh[i]) for(int j=i;j<=b[i];j++) 
			ans+=(!a[j]&&fh[j])+(a[j]&&fg[j]);
	printf("%d\n",ans);
	return 0; 
}