#include <bits/stdc++.h>
using namespace std;
template <typename T>
void maxtt(T& t1, T t2) {
  t1 = max(t1, t2);
}
template <typename T>
void mintt(T& t1, T t2) {
  t1 = min(t1, t2);
}
bool debug = 0;
int n, m, k;
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
string direc = "RDLU";
long long ln, lk, lm;
void etp(bool f = 0) {
  puts(f ? "YES" : "NO");
  exit(0);
}
void addmod(int& x, int y, int mod = 1000000007) {
  assert(y >= 0);
  x += y;
  if (x >= mod) x -= mod;
  assert(x >= 0 && x < mod);
}
void et(int x = -1) {
  printf("%d\n", x);
  exit(0);
}
long long fastPow(long long x, long long y, int mod = 1000000007) {
  long long ans = 1;
  while (y > 0) {
    if (y & 1) ans = (x * ans) % mod;
    x = x * x % mod;
    y >>= 1;
  }
  return ans;
}
long long gcd1(long long x, long long y) { return y ? gcd1(y, x % y) : x; }
long double p[100135], ans, sp;
vector<int> mp[100135];
long double f[100135];
int fa[100135];
void dfs(int x, int pa) {
  fa[x] = pa;
  sp += p[x];
  for (int c : mp[x])
    if (c != pa) {
      dfs(c, x);
      f[x] += p[c];
    }
  ans += p[x] * f[x];
}
void fmain(int tid) {
  scanf("%d", &n);
  for (int(i) = 1; (i) <= (int)(n); (i)++) {
    scanf("%Lf", p + i);
    p[i] = 1 - p[i];
  }
  for (int i = 0; i < n - 1; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u++;
    v++;
    mp[u].push_back(v);
    mp[v].push_back(u);
  }
  dfs(1, 0);
  scanf("%d", &m);
  for (int(i) = 1; (i) <= (int)(m); (i)++) {
    int x;
    long double t;
    scanf("%d%Lf", &x, &t);
    x++;
    t = 1 - t;
    sp -= p[x];
    ans -= p[x] * f[x];
    if (fa[x]) {
      ans -= p[fa[x]] * f[fa[x]];
      f[fa[x]] -= p[x];
      f[fa[x]] += t;
      ans += p[fa[x]] * f[fa[x]];
    }
    p[x] = t;
    sp += p[x];
    ans += p[x] * f[x];
    printf("%.10Lf\n", sp - ans);
  }
}
int main() {
  int t = 1;
  for (int(i) = 1; (i) <= (int)(t); (i)++) {
    fmain(i);
  }
  return 0;
}
