#include<bits/stdc++.h>
using namespace std;
const int N = 2e5 + 15;
// typedef pair<int, int> PII;
vector<int> lead_G, lead_H, ans_G, ans_H;
int n;
int a[N];
string str;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    cin >> n >> str;
    int left_G = N, rigth_G = 0, left_H = N, rigth_H = 0;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
        if(str[i - 1] == 'G') {
            // cnt_G = max(i, cnt_G);
            left_G = min(i, left_G);
            rigth_G = max(i, rigth_G);
        }
        else if(str[i - 1] == 'H') {
            // cnt_H = max(i, cnt_H);
            left_H = min(i, left_H);
            rigth_H = max(i, rigth_G);
        }
    }

    // cout << left_G << " " << rigth_G << endl;
    // cout << left_H << " " << rigth_H << endl;
    for(int i = 1; i <= n; i++) {
        if(str[i - 1] == 'G' && i <= left_G && a[i] >= rigth_G) {
            lead_G.push_back(i);
            ans_G.push_back(i);
        }
        if(str[i - 1] == 'H' && i <= left_H && a[i] >= rigth_H) {
            lead_H.push_back(i);
            ans_H.push_back(i);
        }
    }
    // if(lead_G.size() > 0) sort(lead_G.begin(), lead_G.end());
    // if(lead_H.size() > 0) sort(lead_H.begin(), lead_H.end());

    // for(auto g : lead_G) cout << g << " ";
    // cout << endl;
    // for(auto h : lead_H) cout << h << " ";
    // cout << endl;



    // int ans = 0;
    for(int i = 1; i <= n; i++) {
        if(lead_G.size() > 0 && str[i - 1] == 'H') {
            for(auto g : lead_G) {
                if(i <= g && g <= a[i]) {
                    ans_H.push_back(i);
                    // ans++;
                    // cout << i << endl;
                }
            }
        }

        if(lead_H.size() > 0 && str[i - 1] == 'G') {
            for(auto h : lead_H) {
                if(i <= h && h <= a[i]) {
                    ans_G.push_back(i);
                    // ans++;
                    // cout << i << endl;
                }
            }
        }
    }

    sort(ans_G.begin(), ans_G.end());
    ans_G.erase(unique(ans_G.begin(), ans_G.end()), ans_G.end());

    sort(ans_H.begin(), ans_H.end());
    ans_H.erase(unique(ans_H.begin(), ans_H.end()), ans_H.end());
    // cout << ans << endl;

    int ans = ans_G.size() * ans_H.size();
    cout << ans << endl;


    return 0;
}