#include <bits/stdc++.h>
using namespace std;
int n, m, x, y, tot, head[100000], fa[100000];
double z, son[100000], a[100000], ans;
struct edge {
  int v, nxt;
} e[100000];
void add(int x, int y) {
  e[++tot].v = y;
  e[tot].nxt = head[x];
  head[x] = tot;
}
void dfs(int u) {
  for (int i = head[u], v; i; i = e[i].nxt)
    if ((v = e[i].v) != fa[u]) {
      fa[v] = u;
      dfs(v);
      son[u] += 1 - a[v];
    }
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%lf", a + i);
  for (int i = 1; i < n; ++i) {
    scanf("%d%d", &x, &y);
    add(++x, ++y);
    add(y, x);
  }
  dfs(1);
  scanf("%d", &m);
  a[0] = 1;
  for (int i = 1; i <= n; ++i) ans += a[fa[i]] * (1 - a[i]);
  while (m--) {
    scanf("%d%lf", &x, &z);
    ++x;
    ans -= a[fa[x]] * (1 - a[x]) + a[x] * son[x];
    son[fa[x]] -= 1 - a[x];
    a[x] = z;
    ans += a[fa[x]] * (1 - a[x]) + a[x] * son[x];
    son[fa[x]] += 1 - a[x];
    printf("%.8lf\n", ans);
  }
  return 0;
}
