#include <bits/stdc++.h>
#define all(a) a.begin(), a.end()
using namespace std;
typedef long double ld;
int k;
string s;
vector<ld> arr;
vector<int> nextes;
ld dfs(int l, int r) {
if (r - l == 2)
return arr[0];
stack<int> opens;
vector<ld> maxis;
char sign = '+';
for (int i = l + 1; i < r; i++) {
if (s[i] == '(')
{
int nxt = nextes[i];
if (maxis.empty())
sign = s[nxt + 1];
maxis.push_back(dfs(i, nxt));
i = nxt;
}
}
if (sign == '+') {
return min(arr[maxis.size() - 1], accumulate(all(maxis), (ld)0.0));
}
sort(all(maxis));
ld max_sum = arr[maxis.size() - 1];
ld prod = 1;
ld sum_all = accumulate(all(maxis), ld(0));
bool flag = false; ld val = -1;
for (int i = 0; i < maxis.size(); i++) {
ld left = maxis.size() - i;
if (maxis[i] < max_sum / left and !flag) {
prod *= maxis[i];
sum_all -= maxis[i];
max_sum -= maxis[i];
} else if (!flag) {
flag = true;
val = max_sum / left;
}
if (flag)
prod *= val;
}
return prod;
}
int main()
{
cin >> k;
arr = vector<ld> (k);
for (int i = 0; i < k; i++)
cin >> arr[i];
cin >> s;
nextes.resize(s.size());
stack<int> opens;
vector<ld> maxis;
char sign = '+';
for (int i = 0; i < s.size(); i++) {
if (s[i] == '(')
opens.push(i);
else if (s[i] == ')') {
int idx = opens.top();
opens.pop();
nextes[idx] = i;
}
}
int cnt = 0;
cout << fixed << setprecision(10) << dfs(0, s.size() - 1) << "\n";
return 0;
}
