Problem:
Bridge Removal

ICPC islands once had been a popular tourist destination.
For nature preservation, however, the government decided to prohibit entrance to the islands,
and to remove all the man-made structures there.
The hardest part of the project is to remove all the bridges connecting the islands.

There are n islands and n-1 bridges.
The bridges are built so that all the islands are reachable from all the other islands by
crossing one or more bridges.
The bridge removal team can choose any island as the starting point, and can repeat either of the
following steps.

Move to another island by crossing a bridge that is connected to the current island.

Remove one bridge that is connected to the current island, and stay at the same island after the removal.

Of course, a bridge, once removed, cannot be crossed in either direction.
Crossing or removing a bridge both takes time proportional to the length of the bridge.
Your task is to compute the shortest time necessary for removing all the bridges.
Note that the island where the team starts can differ from where the team finishes the work.

Input

The input consists of at most 100 datasets.
Each dataset is formatted as follows.

n

p2 p3 ... pn

d2 d3 ... dn

The first integer n (3 ≤ n ≤ 800) is the number of the islands.
The islands are numbered from 1 to n.
The second line contains n-1 island numbers pi
(1 ≤ pi < i), and tells that for each i
from 2 to n the island i and the island pi are connected by a bridge.
The third line contains n-1 integers di (1 ≤ di ≤ 100,000)
each denoting the length of the corresponding bridge.
That is, the length of the bridge connecting the island i and pi
is di. It takes di units of time to cross the bridge, and
also the same units of time to remove it.

Note that, with this input format, it is assured that all the islands are reachable each other by
crossing one or more bridges.

The input ends with a line with a single zero.

Output

For each dataset, print the minimum time units required to remove all the bridges in a single line.
Each line should not have any character other than this number.

Sample Input

4
1 2 3
10 20 30
10
1 2 2 1 5 5 1 8 8
10 1 1 20 1 1 30 1 1
3
1 1
1 1
0

Output for the Sample Input

80
136
2

Solution in C# (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Trace;
using SB = System.Text.StringBuilder;
using Number = System.Int64;
namespace Program
{
    public class Solver
    {
        public void Solve()
        {
            for (; ; )
            {
                var n = ri;
                if (n == 0) return;
                var G = Enumerate(n, x => new List<KeyValuePair<int, long>>());
                var p = Enumerate(n - 1, x => ri - 1);
                var d = Enumerate(n - 1, x => ri);
                for (int i = 0; i < n - 1; i++)
                {
                    G[i + 1].Add(new KeyValuePair<int, Number>(p[i], d[i]));
                    G[p[i]].Add(new KeyValuePair<int, Number>(i + 1, d[i]));
                }
                long sum = 3 * d.Sum();
                for (int i = 0; i < n; i++)
                    if (G[i].Count == 1) sum -= 2 * G[i].First().Value;
                long max = 0;
                for (int i = 0; i < n; i++)
                    max = Math.Max(max, dfs(-1, i, 0, G));
                Console.WriteLine(sum - max);
            }
        }
        long dfs(int prev, int cur, long d, List<KeyValuePair<int, long>>[] G)
        {
            var max = d;
            if (G[cur].Count == 1) return 0;
            foreach (var t in G[cur])
            {
                if (t.Key == prev) continue;
                max = Math.Max(max, dfs(cur, t.Key, d + t.Value, G));
            }
            return max;
        }
        const long INF = 1L << 60;
        //int[] dx = { -1, 0, 1, 0 };
        //int[] dy = { 0, 1, 0, -1 };
        //*
        int ri { get { return sc.Integer(); } }
        long rl { get { return sc.Long(); } }
        double rd { get { return sc.Double(); } }
        string rs { get { return sc.Scan(); } }
        //*/

        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex
{
    static public string AsString(this IEnumerable<char> ie) { return new string(ie.ToArray()); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ")
    {
        return string.Join(st, ie.Select(x => x.ToString()).ToArray());
        //return string.Join(st, ie);
    }
    static public void Main()
    {
        Console.SetOut(new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Program.Solver();
        solver.Solve();
        Console.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer: StreamWriter
    {
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n' && b != 0; b = (char)read())
                if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long() { return isEof ? long.MinValue : long.Parse(Scan()); }
        public int Integer() { return isEof ? int.MinValue : int.Parse(Scan()); }
        public double Double() { return isEof ? double.NaN : double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
}
#endregion