#include<bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using pi = pair<int,int>;
typedef long long ll;
#define debug(x) cout << #x << " = " << x << "\n";
#define vdebug(a) cout << #a << " = "; for(auto x: a) cout << x << " "; cout << "\n";
const int MOD = 998244353;
const int N = (int)2e5 + 5;
template<ll mod>
struct modnum {
static constexpr bool is_big_mod = mod > numeric_limits<int>::max();
using S = conditional_t<is_big_mod, ll, int>;
using L = conditional_t<is_big_mod, __int128, ll>;
S x;
modnum() : x(0) {}
modnum(ll _x) {
_x %= static_cast<ll>(mod);
if (_x < 0) { _x += mod; }
x = _x;
}
modnum pow(ll n) const {
modnum res = 1;
modnum cur = *this;
while (n > 0) {
if (n & 1) res *= cur;
cur *= cur;
n /= 2;
}
return res;
}
modnum inv() const { return (*this).pow(mod-2); }
modnum& operator+=(const modnum& a){
x += a.x;
if (x >= mod) x -= mod;
return *this;
}
modnum& operator-=(const modnum& a){
if (x < a.x) x += mod;
x -= a.x;
return *this;
}
modnum& operator*=(const modnum& a){
x = static_cast<L>(x) * a.x % mod;
return *this;
}
modnum& operator/=(const modnum& a){ return *this *= a.inv(); }
friend modnum operator+(const modnum& a, const modnum& b){ return modnum(a) += b; }
friend modnum operator-(const modnum& a, const modnum& b){ return modnum(a) -= b; }
friend modnum operator*(const modnum& a, const modnum& b){ return modnum(a) *= b; }
friend modnum operator/(const modnum& a, const modnum& b){ return modnum(a) /= b; }
friend bool operator==(const modnum& a, const modnum& b){ return a.x == b.x; }
friend bool operator!=(const modnum& a, const modnum& b){ return a.x != b.x; }
friend bool operator<(const modnum& a, const modnum& b){ return a.x < b.x; }
friend ostream& operator<<(ostream& os, const modnum& a){ os << a.x; return os; }
friend istream& operator>>(istream& is, modnum& a) { ll x; is >> x; a = modnum(x); return is; }
};
using mint = modnum<MOD>;
template <class T> struct SegTree{
vector<T> seg;
int n;
const T ID = 0;
T cmb(T a, T b){
return max(a, b);
}
SegTree(int _n){
n = 1;
while (n < _n) n *= 2;
seg.assign(2 * n + 1, ID);
}
void set(int pos, T val){
seg[pos + n] = val;
}
void build(){
for (int i = n - 1; i >= 1; i--) seg[i] = cmb(seg[2 * i], seg[2 * i + 1]);
}
void upd(int v, int tl, int tr, int pos, T val){
if (tl == tr){
seg[v] = val;
} else {
int tm = (tl + tr) / 2;
if (pos <= tm) upd(2 * v, tl, tm, pos, val);
else upd(2 * v + 1, tm + 1, tr, pos, val);
seg[v] = cmb(seg[2 * v], seg[2 * v + 1]);
}
}
void upd(int pos, T val){
upd(1, 0, n - 1, pos, val);
}
T query(int v, int tl, int tr, int l, int r){
if (l > r) return ID;
if (l == tl && r == tr) return seg[v];
int tm = (tl + tr) / 2;
T res = query(2 * v, tl, tm, l, min(tm, r));
res = cmb(res, query(2 * v + 1, tm + 1, tr, max(l, tm + 1), r));
return res;
}
T query(int l, int r){
return query(1, 0, n - 1, l, r);
}
};
int grps;
struct DSU{
vector<int> p, sz, used, mn, mx;
DSU(int n){
p.assign(n, 0);
sz.assign(n, 1);
used.assign(n, 0);
mx.assign(n, 0);
mn.assign(n, 0);
for (int i = 0; i < n; i++) p[i] = i;
}
int find(int u){
if (p[u] == u) return u;
p[u] = find(p[u]);
return p[u];
}
void unite(int u, int v){
u = find(u);
v = find(v);
if (u == v) return;
--grps;
if (sz[u] < sz[v]) swap(u, v);
p[v] = u;
sz[u] += sz[v];
used[u] += used[v];
mn[u] = min(mn[u], mn[v]);
mx[u] = max(mx[u], mx[v]);
}
bool same(int u, int v){
return find(u) == find(v);
}
int size(int u){
u = find(u);
return sz[u];
}
};
struct BIT {
int b[N], n;
void init(int _n) {
n = _n;
for(int i = 0 ; i <= n ; ++i) b[i] = 0;
}
inline int lowbit(int x) { return x & (-x); }
void update(int x, int v) {
for(int i = x ; i <= n ; i += lowbit(i)) b[i] += v;
}
int query(int x) {
int ans = 0;
for(int i = x ; i > 0 ; i -= lowbit(i)) ans += b[i];
return ans;
}
} bit;
int k;
vi z;
vector<int>E[N];
vector<float>v;
float add(int pos) {
if(E[pos].empty()) return z[0];
float sum = 0;
for(int x: E[pos]) sum += v[x];
int siz = (int)E[pos].size();
return min(sum, (float)z[siz-1]);
}
float mul(int pos) {
if(E[pos].empty()) return z[0];
vector<float>V;
for(int x: E[pos]) {
V.push_back(v[x]);
}
sort(V.begin(), V.end());
int siz = (int)E[pos].size();
float sum = z[siz-1], ans = 1;
for(float x: V) {
float exp = sum / siz;
if(x < exp) {
sum -= x;
ans *= x;
--siz;
} else {
for(int j=0; j<siz; ++j) ans *= exp;
break;
}
}
return ans;
}
void solve() {
cin >> k;
for(int i=0; i<k; ++i) {
int tmp;
cin >> tmp;
z.push_back(tmp);
}
v.assign(N, z[0]);
string str;
cin >> str;
stack<int>s;
int cnt = 0, op = 0;
for(char c: str) {
if(c == '(') {
if(!s.empty()) E[s.top()].push_back(cnt);
s.push(cnt);
++cnt;
} else if(c == '+') op = 0;
else if(c == '*') op = 1;
else if(c == ')') {
int cur = s.top();
s.pop();
if(!op) v[cur] = add(cur);
else v[cur] = mul(cur);
}
}
cout << fixed << setprecision(4) << v[0] << endl;
}
int main(){
int t = 1;
while (t--) solve();
}
