#include<bits/stdc++.h>
#define int long long
#define deg(a) cout << #a << " = " << a << "\n";
#define de(a) cout << #a << " = " << a << " ";
#define x first
#define y second

using namespace std;
const int N=1e5+10;
int a[N],b[N];
signed main()
{
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout.tie(0);
//    fstream cin;
//    cin.open("in.txt",ios::in);
    int n;
    cin>>n;
    string s;
    cin>>s;
    s=" "+s;
    for(int i=1;i<=n;i++)
    {
        if(s[i]=='G')a[i]=1;
        else a[i]=0;
    }
    for(int i=1;i<=n;i++)cin>>b[i];
    int ga,gb,ha,hb;
    for(int i=1;i<=n;i++)
        if(a[i]==1)
        {
            ga=i;
            break;
        }
    for(int i=1;i<=n;i++)
        if(a[i]==0)
        {
            ha=i;
            break;
        }
    for(int i=n;i>=1;i--)
        if(a[i]==1)
        {
            gb=i;
            break;
        }
    for(int i=n;i>=1;i--)
        if(a[i]==0)
        {
            hb=i;
            break;
        }
    int ans=0;
    if(b[ga]>=gb&&b[ha]>=hb)ans++;
    int ok=1;
    for(int i=1;i<=n;i++)
    {
        if(i<ga&&a[i]==0&&b[i]>=ga)
        {
            if(i==ha&&b[ga]>=gb&&b[ha]>=hb)ok=0;
            ans++;
        }
        if(i<ha&&a[i]==1&&b[i]>=ha)
        {
            if(i==ga&&b[ga]>=gb&&b[ha]>=hb)ok=0;
            ans++;
        }
    }
    if(!ok)ans--;
    cout<<ans<<endl;
    return 0;
}