#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int FFTMOD = 119 << 23 | 1;
const int INF = (int)1e9 + 23111992;
const long long LINF = (long long)1e18 + 23111992;
const long double PI = acos((long double)-1);
const long double EPS = 1e-9;
inline long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
inline long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
inline int chkmin(T& a, const T& val) {
  return val < a ? a = val, 1 : 0;
}
template <class T>
inline int chkmax(T& a, const T& val) {
  return a < val ? a = val, 1 : 0;
}
inline unsigned long long isqrt(unsigned long long k) {
  unsigned long long r = sqrt(k) + 1;
  while (r * r > k) r--;
  return r;
}
inline long long icbrt(long long k) {
  long long r = cbrt(k) + 1;
  while (r * r * r > k) r--;
  return r;
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(long double x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(long double x, long double y) { return sign(x - y); }
mt19937 mt(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int myrand() { return abs((int)mt()); }
const int maxn = 1e5 + 5;
const int magic = 500;
int n;
double a[maxn];
double b[maxn];
vector<pair<int, int> > edges;
vector<int> adj[maxn];
void chemthan() {
  cin >> n;
  for (int i = (0); i < (n); ++i) cin >> a[i];
  for (int i = (0); i < (n - 1); ++i) {
    int u, v;
    cin >> u >> v;
    edges.push_back(make_pair(u, v));
    adj[u].push_back(v), adj[v].push_back(u);
    b[u] += a[v];
    b[v] += a[u];
  }
  vector<int> ver;
  for (int i = (0); i < (n); ++i)
    if (int((adj[i]).size()) >= magic) ver.push_back(i);
  for (int i = (0); i < (n); ++i) sort((adj[i]).begin(), (adj[i]).end());
  double sum = 0.0, sum2 = 0.0;
  for (int i = (0); i < (n); ++i) sum += a[i];
  for (int i = (0); i < (n - 1); ++i) {
    int u = edges[i].first;
    int v = edges[i].second;
    sum2 += a[u] + a[v] - a[u] * a[v];
  }
  int q;
  cin >> q;
  while (q--) {
    int u;
    double v;
    cin >> u >> v;
    double res = 1.0 - sum + sum2;
    if (int((adj[u]).size()) >= magic) {
      res -= int((adj[u]).size()) - (1 - a[u]) * (int((adj[u]).size()) - b[u]);
      sum2 -= int((adj[u]).size()) - (1 - a[u]) * (int((adj[u]).size()) - b[u]);
    } else {
      for (int v : adj[u]) {
        res -= 1 - (1 - a[u]) * (1 - a[v]);
        sum2 -= 1 - (1 - a[u]) * (1 - a[v]);
      }
    }
    for (int w : ver) {
      int k = lower_bound((adj[u]).begin(), (adj[u]).end(), w) - adj[u].begin();
      if (k < int((adj[u]).size()) && adj[u][k] == w) {
        b[w] -= a[u];
      }
    }
    sum -= a[u];
    res += a[u];
    a[u] = v;
    sum += a[u];
    res -= a[u];
    if (int((adj[u]).size()) >= magic) {
      res += int((adj[u]).size()) - (1 - a[u]) * (int((adj[u]).size()) - b[u]);
      sum2 += int((adj[u]).size()) - (1 - a[u]) * (int((adj[u]).size()) - b[u]);
    } else {
      for (int v : adj[u]) {
        res += 1 - (1 - a[u]) * (1 - a[v]);
        sum2 += 1 - (1 - a[u]) * (1 - a[v]);
      }
    }
    for (int w : ver) {
      int k = lower_bound((adj[u]).begin(), (adj[u]).end(), w) - adj[u].begin();
      if (k < int((adj[u]).size()) && adj[u][k] == w) {
        b[w] += a[u];
      }
    }
    cout << fixed << setprecision(9) << res << "\n";
  }
}
int main(int argc, char* argv[]) {
  ios_base::sync_with_stdio(0), cin.tie(0);
  if (argc > 1) {
    assert(freopen(argv[1], "r", stdin));
  }
  if (argc > 2) {
    assert(freopen(argv[2], "wb", stdout));
  }
  chemthan();
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}
