#include<bits/stdc++.h>
using namespace std;
int species[100010],area[100010];
int n,fg,fh,gmax,hmax,ans=0;
int main(){
	freopen("leaders.in","r",stdin);
	freopen("leaders.out","w",stdout);
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	char c;
	for(int i=1;i<=n;i++){
		cin>>c;
		if(c=='G'){
			species[i]=1;
			gmax=i;
		}
		else{
			species[i]=2;
			hmax=i;
		}
	}
	for(int i=1;i<=n;i++){
		cin>>area[i];
	}
	for(int i=1;i<=n;i++){
		if(species[i]==2){
			continue;
		}
		if(area[i]>=gmax){
			fg=i;
		}
		break;
	}
	for(int i=1;i<=n;i++){
		if(species[i]==1){
			continue;
		}
		if(area[i]>=hmax){
			fh=i;
		}
		break;
	}
	for(int i=1;i<=n;i++){
		if((fg&&species[i]==2&&i<fg&&area[i]>=fg)||(fh&&species[i]==1&&i<fh&&area[i]>=fh)){
			ans++;
		}
	}
	if(fg&&fh&&area[min(fg,fh)]<max(fg,fh)){
		ans++;
	}
	cout<<ans<<endl;
    return 0;
}