#include<bits/stdc++.h>
#define ll long long
using namespace std; 
const ll N=1e5+10;
ll a[N],n,g=0,h=0,G=0,H=0,ans=0;
string s;
char ch;
bool x=0,y=0;
int main()
{ 
	freopen("leaders.in","r",stdin);
	freopen("leaders.out","w",stdout);
    cin>>n>>s;
    s=' '+s;
    for(ll i=1;i<s.size();i++){
        if(s[i]=='G'&&!g)g=i;
        else if(s[i]=='H'&&!h)h=i;
    }
    for(ll i=s.size()-1;i>=1;i--){
        if(s[i]=='G'&&!G)G=i;
        else if(s[i]=='H'&&!H)H=i;
    }
    for(ll i=1;i<=n;i++)cin>>a[i];
    for(ll i=1;i<=n;i++){
        if(s[i]=='G'){
            if(a[i]>=h&&i<=h&&a[h]>=H){
            	ans++;
            	if(i==g)x=1;
            }
        }
        if(s[i]=='H'){
            if(a[i]>=g&&i<=g&&a[g]>=G){
            	ans++;
            	if(i==h)y=1;
            }
        }
    }
    if(a[g]>=G&&a[h]>=H&&!x&&!y)ans++;
    cout<<ans;
    return 0;
}