import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        ScanReader in = new ScanReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        DInterstellarBattle solver = new DInterstellarBattle();
        solver.solve(1, in, out);
        out.close();
    }

    static class DInterstellarBattle {
        double[] pfall;
        double[] palive;
        double[] contributionofparent;
        int[] par;
        ArrayList<Integer>[] arrayList;

        void DFS(int s, int p) {
            par[s] = p;
            double temp = 0;
            for (int tt : arrayList[s]) {
                if (p != tt) {
                    DFS(tt, s);
                    temp += palive[tt];
                }
            }
            contributionofparent[s] = temp;
        }

        public void solve(int testNumber, ScanReader in, PrintWriter out) {
            int n = in.scanInt();
            arrayList = new ArrayList[n + 1];
            par = new int[n + 1];
            pfall = new double[n + 1];
            palive = new double[n + 1];
            contributionofparent = new double[n + 1];
            for (int i = 0; i <= n; i++) {
                arrayList[i] = new ArrayList<>();
            }

            for (int i = 1; i <= n; i++) {
                pfall[i] = in.scanDouble();
                palive[i] = 1 - pfall[i];
            }

            for (int i = 0; i < n - 1; i++) {
                int x = in.scanInt() + 1;
                int y = in.scanInt() + 1;
                arrayList[x].add(y);
                arrayList[y].add(x);
            }
            Arrays.fill(par, -1);
            DFS(1, 0);
            palive[0] = 1;
            pfall[0] = 0;
            contributionofparent[0] = palive[1];
            int q = in.scanInt();


            double ans = 0;
            for (int i = 1; i <= n; i++) {
                ans += pfall[i] * contributionofparent[i];
            }
            ans += palive[1];

            while (q-- > 0) {
                int p = in.scanInt() + 1;
                if (p != 1) {
                    ans -= contributionofparent[par[p]] * pfall[par[p]];
                    ans -= pfall[p] * contributionofparent[p];
                    contributionofparent[par[p]] -= palive[p];
                    pfall[p] = in.scanDouble();
                    palive[p] = 1 - pfall[p];
                    contributionofparent[par[p]] += palive[p];
                    ans += contributionofparent[par[p]] * pfall[par[p]];
                    ans += pfall[p] * contributionofparent[p];
                    out.printf("%.5f\n", ans);
                } else {
                    ans -= pfall[1] * contributionofparent[1];
                    ans -= palive[1];
                    pfall[p] = in.scanDouble();
                    palive[p] = 1 - pfall[p];
                    ans += pfall[1] * contributionofparent[1];
                    ans += palive[1];
                    out.printf("%.5f\n", ans);

                }


            }
        }

    }

    static class ScanReader {
        private byte[] buf = new byte[4 * 1024];
        private int INDEX;
        private BufferedInputStream in;
        private int TOTAL;

        public ScanReader(InputStream inputStream) {
            in = new BufferedInputStream(inputStream);
        }

        private int scan() {
            if (INDEX >= TOTAL) {
                INDEX = 0;
                try {
                    TOTAL = in.read(buf);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                if (TOTAL <= 0) return -1;
            }
            return buf[INDEX++];
        }

        public int scanInt() {
            int I = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    I *= 10;
                    I += n - '0';
                    n = scan();
                }
            }
            return neg * I;
        }

        private boolean isWhiteSpace(int n) {
            if (n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1) return true;
            else return false;
        }

        public double scanDouble() {
            int c = scan();
            while (isWhiteSpace(c)) c = scan();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = scan();
            }
            double RESULT = 0;
            while (!isWhiteSpace(c) && c != '.') {
                if (c == 'e' || c == 'E') {
                    return RESULT * Math.pow(10, scanInt());
                }
                RESULT *= 10;
                RESULT += c - '0';
                c = scan();
            }
            if (c == '.') {
                c = scan();
                double m = 1;
                while (!isWhiteSpace(c)) {
                    if (c == 'e' || c == 'E') {
                        return RESULT * Math.pow(10, scanInt());
                    }
                    m /= 10;
                    RESULT += (c - '0') * m;
                    c = scan();
                }
            }
            return RESULT * sgn;
        }

    }
}

