#include <bits/stdc++.h>
using namespace std;
template <typename T>
bool get_int(T &x) {
  char t = getchar();
  bool neg = false;
  x = 0;
  for (; (t > '9' || t < '0') && t != '-' && t != EOF; t = getchar())
    ;
  if (t == '-') neg = true, t = getchar();
  if (t == EOF) return false;
  for (; t <= '9' && t >= '0'; t = getchar()) x = x * 10 + t - '0';
  if (neg) x = -x;
  return true;
}
template <typename T>
void print_int(T x) {
  if (x < 0) putchar('-'), x = -x;
  short a[20] = {}, sz = 0;
  while (x > 0) a[sz++] = x % 10, x /= 10;
  if (sz == 0) putchar('0');
  for (int i = sz - 1; i >= 0; i--) putchar('0' + a[i]);
}
const int inf = 0x3f3f3f3f;
const long long Linf = 1ll << 61;
const double pi = acos(-1.0);
const int maxn = 100111;
long long l[maxn];
int n;
char s[maxn];
int main() {
  get_int(n);
  for (int i = 1; i <= n; i++) get_int(l[i]);
  scanf("%s", s + 1);
  int have = inf;
  long long ws = 0, ww = 0, ans = 0;
  for (int i = 1; i <= n; i++) {
    ans += l[i];
    if (s[i] == 'W') ws += l[i] + l[i], have = min(have, 3);
    if (s[i] == 'G') ww += l[i] + l[i], have = min(have, 5);
    long long cur = l[i], now = 0;
    now = min(cur, ws);
    ans += now;
    ws -= now;
    cur -= now;
    now = min(cur, ww);
    ans += now * 2;
    ww -= now;
    cur -= now;
    ans += cur * have;
  }
  print_int(ans), puts("");
  return 0;
}
