#include<bits/stdc++.h>
using namespace std;
int n, a[100010], b[100010], st[2], pos[2], ok[2], cs[2][100010], cnt[2], ans;
string s;
int main() {
	freopen("leaders.in", "r", stdin);
	freopen("leaders.out", "w", stdout);
	cin >> n >> s;
	for(int i = 1; i <= n; i ++) {
		cin >> a[i];
		if(s[i - 1] == 'G') {
			b[i] = 1;
		}
		if(!st[b[i]]) {
			st[b[i]] = i;
		}
		pos[b[i]] = i;
	}
	if(a[st[0]] >= pos[0]) {
		ok[0] = 1;
	}
	if(a[st[1]] >= pos[1]) {
		ok[1] = 1;
	}
	if(ok[0] && ok[1]) {
		ans ++;
	}
	for(int i = 1; i <= n; i ++) {
		if(a[i] >= st[!b[i]] && i <= st[!b[i]] && ok[!b[i]]) {
			ans ++;
		}
	}
	cout << ans;
	return 0;
}