using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using SB = System.Text.StringBuilder;
using Number = System.Int64;
using System.Numerics;
using static System.Math;
namespace Program {
    public class Solver {
        Random rnd = new Random(0);
        public void Solve() {
            var n = ri;

            var a = Enumerate(n, x => new long[] { rl, rl }).ToList();
            if (n % 2 == 0) { n++; a.Add(new long[] { 0, 0 }); }
            a.Sort((l, r) => (l[0] + l[1]).CompareTo(r[0] + r[1]));
            a.Reverse();
            //左側に動かすコスト Σi*Len_{i} + Σr_i
            //右側に動かすコスト Σi*Len_{i} + Σl_i

            //すでに i 個左に置かれていて，中心に置いたかどうか
            var dp = new long[n + 5, 2];
            for (int i = 0; i < n + 5; i++)
                for (int j = 0; j < 2; j++)
                    dp[i, j] = INF;
            dp[0, 0] = 0;
            var cnt = 0;
            foreach (var x in a)
            {
                var l = x[0];
                var r = x[1];
                var len = x[0] + x[1];
                Debug.WriteLine(len);
                var next = new long[n + 5, 2];
                for (int i = 0; i < n + 5; i++)
                    for (int j = 0; j < 2; j++)
                        next[i, j] = INF;
                for (int j = 0; j < 2; j++)
                    for (int i = 0; i + j <= cnt; i++)
                    {
                        var k = cnt - j - i;
                        //left
                        next[i + 1, j] = Math.Min(next[i + 1, j], dp[i, j] + i * len + r);
                        //right
                        next[i, j] = Math.Min(next[i, j], dp[i, j] + k * len + l);
                        //center
                        if (j == 0) next[i, j + 1] = Math.Min(next[i, j + 1], dp[i, j] + len * (n - 1) / 2);

                    }
                cnt++;
                dp = next;
            }
            Console.WriteLine(dp[(n - 1) / 2, 1]);
        }
        const long INF = 1L << 60;
        static int[] dx = { -1, 0, 1, 0 };
        static 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);
    }

    static public void Main() {
        Console.SetOut(new Program.IO.Printer(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Program.Solver();
        try
        {
            solver.Solve();
            Console.Out.Flush();
        }
        catch { }
    }
}
#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


Measured memory_bytes: 30456