using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using Number = System.Int64;
using static System.Math;
using P = Pair<long, long>;
namespace Program
{
public class Solver
{
const int B = 32;
const long M = (1L << 32) - 1;
const long U = ~M;
public void Solve()
{
var n = ri;
var G = Enumerate(n, x => new List<KeyValuePair<int, int>>());
for (int i = 0; i < n - 1; i++)
{
var a = ri - 1;
var b = i + 1;
var w = ri;
G[a].Add(new KeyValuePair<int, int>(b, w));
}
Func<List<P>, List<P>, List<P>> g = (a, b) =>
{
var ret = new List<P>();
var min = 1000000000000000;
int i = 0, j = 0;
while (i < a.Count && j < b.Count)
{
var l = a[i];
var r = b[j];
if (min <= l.y) { i++; continue; }
if (min <= r.y) { j++; continue; }
if (l.CompareTo(r) <= 0) { i++; min = l.y; ret.Add(l); }
else { j++; min = r.y; ret.Add(r); }
}
while (i < a.Count)
{
if (min <= a[i].y) i++;
else { min = a[i].y; ret.Add(a[i++]); }
}
while (j < b.Count)
{
if (min <= b[j].y) j++;
else { min = b[j].y; ret.Add(b[j++]); }
}
return ret;
};
var s = Enumerate(n, x => new List<P>());
Func<long, bool> f = null;
f = x =>
{
for (int cur = n - 1; cur >= 0; cur--)
{
if (G[cur].Count == 0) { s[cur] = new List<P>() { new P(0, 0) }; continue; }
var l = s[G[cur][0].Key];
var r = s[G[cur][1].Key];
if (l.Count == 0) return false;
if (r.Count == 0) return false;
var u = G[cur][0].Value;
var v = G[cur][1].Value;
var a = new List<P>();
var b = new List<P>();
if (l.Count > r.Count) { Swap(ref l, ref r); Swap(ref u, ref v); }
var i = 0; var j = 0; var k = 0;
while (i < l.Count)
{
while (j < r.Count && l[i].x + r[j].y + u + v > x) j++;
while (k + 1 < r.Count && l[i].y + r[k + 1].x + u + v <= x) k++;
if (k < r.Count && l[i].y + r[k].x + u + v <= x) a.Add(new P(l[i].x + u, r[k].y + v));
if (j < r.Count) b.Add(new P(r[j].x + v, l[i].y + u));
i++;
}
s[cur] = g(a, b);
}
//Debug.WriteLine($"[{cur}], {ret.AsJoinedString()}");
return s[0].Count > 0;
};
{
long l = -1, r = 100000000;
while (r - l > 1)
{
var m = (l + r) / 2;
if (f(m)) r = m;
else l = m;
}
IO.Printer.Out.WriteLine(r);
}
}
int ri => sc.Integer();
long rl => sc.Long();
double rd => sc.Double();
string rs => 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(System.Linq.Enumerable.ToArray(ie)); }
static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
static public void Main()
{
var solver = new Program.Solver();
solver.Solve();
Program.IO.Printer.Out.Flush();
}
}
#endregion
#region Ex
namespace Program.IO
{
using System.IO;
using System.Text;
using System.Globalization;
public class Printer: StreamWriter
{
static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
public static Printer Out { get; set; }
public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
}
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 = (char)read())
if (b == 0) break;
else if (b != '\r') sb.Append(b);
return sb.ToString();
}
public long Long()
{
if (isEof) return long.MinValue;
long ret = 0; byte b = 0; var ng = false;
do b = read();
while (b != 0 && b != '-' && (b < '0' || '9' < b));
if (b == 0) return long.MinValue;
if (b == '-') { ng = true; b = read(); }
for (; true; b = read())
{
if (b < '0' || '9' < b)
return ng ? -ret : ret;
else ret = ret * 10 + b - '0';
}
}
public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
private T[] enumerate<T>(int n, Func<T> f)
{
var a = new T[n];
for (int i = 0; i < n; ++i) a[i] = f();
return a;
}
public char[] Char(int n) { return enumerate(n, Char); }
public string[] Scan(int n) { return enumerate(n, Scan); }
public double[] Double(int n) { return enumerate(n, Double); }
public int[] Integer(int n) { return enumerate(n, Integer); }
public long[] Long(int n) { return enumerate(n, Long); }
}
}
#endregion
#region Compair
static public class Pair
{
static public Pair<FT, ST> Create<FT, ST>(FT f, ST s) where FT : IComparable<FT> where ST : IComparable<ST>
{
return new Pair<FT, ST>(f, s);
}
static public Pair<FT, ST> Min<FT, ST>(Pair<FT, ST> p, Pair<FT, ST> q) where FT : IComparable<FT> where ST : IComparable<ST>
{
return (p.CompareTo(q) <= 0) ? p : q;
}
static public Pair<FT, ST> Max<FT, ST>(Pair<FT, ST> p, Pair<FT, ST> q) where FT : IComparable<FT> where ST : IComparable<ST>
{
return (p.CompareTo(q) >= 0) ? p : q;
}
}
public struct Pair<FT, ST>: IComparable<Pair<FT, ST>> where FT : IComparable<FT> where ST : IComparable<ST>
{
public FT x;
public ST y;
public Pair(FT f, ST s) : this() { x = f; y = s; }
public int CompareTo(Pair<FT, ST> other)
{
var cmp = x.CompareTo(other.x);
return cmp != 0 ? cmp : y.CompareTo(other.y);
}
public override string ToString() { return string.Format("[{0} {1}]", x, y); }
}
#endregion