Problem:
Huffman Coding

We want to encode a given string $S$ to a binary string. Each alphabet character in $S$ should be mapped to a different variable-length code and the code must not be a prefix of others.

Huffman coding is known as one of ways to obtain a code table for such encoding.

For example, we consider that appearance frequencycies of each alphabet character in $S$ are as follows:

a

b

c

d

e

f

freq.

45

13

12

16

9

5

code

0

101

100

111

1101

1100

We can obtain "Huffman codes" (the third row of the table) using Huffman's algorithm.

The algorithm finds a full binary tree called "Huffman tree" as shown in the following figure.

To obtain a Huffman tree, for each alphabet character, we first prepare a node which has no parents and a frequency (weight) of the alphabet character. Then, we repeat the following steps:

Choose two nodes, $x$ and $y$, which has no parents and the smallest weights.

Create a new node $z$ whose weight is the sum of $x$'s and $y$'s.

Add edge linking $z$ to $x$ with label $0$ and to $y$ with label $1$. Then $z$ become their parent.

If there is only one node without a parent, which is the root, finish the algorithm. Otherwise, go to step 1.

Finally, we can find a "Huffman code" in a path from the root to leaves.

Task

Given a string $S$, output the length of a binary string obtained by using Huffman coding for $S$.

Input

$S$

A string $S$ is given in a line.

Output

Print the length of a binary string in a line.

Constraints

$1 \le |S| \le 10^5$

$S$ consists of lowercase English letters.

Sample Input 1

abca

Sample Output 1

6

Sample Input 2

aaabbcccdeeeffg

Sample Output 2

41

Sample Input 3

z

Sample Output 3

1

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using SB = System.Text.StringBuilder;
//using System.Text.RegularExpressions;
//using System.Globalization;
//using System.Diagnostics;
using static System.Console;
using System.Numerics;
using static System.Math;
using pair = Pair<int, int>;

class Program
{
    static void Main()
    {
        //SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
        new Program().solve();
        Out.Flush();
    }
    readonly Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 }; //→↓←↑
    readonly int mod = 1000000007;
    readonly int dom = 998244353;
    bool chmax<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
    bool chmin<T>(ref T a, T b) where T : IComparable<T> { if (b.CompareTo(a) < 0) { a = b; return true; } return false; }

    void solve()
    {
        var S = ReadLine();

        var A = new int[26];
        foreach (var item in S)
        {
            A[item - 'a']++;
        }
        var P = new PriorityQueue<Node>(-1);
        foreach (var v in A)
        {
            if (v > 0) P.Enqueue(new Node(v));
        }
        if (P.Count == 1)
        {
            WriteLine(P.Peek().occurrence);
            return;
        }

        while (P.Count > 1)
        {
            var d = P.Dequeue();
            var e = P.Dequeue();
            var node = new Node(d.occurrence + e.occurrence) { l = d, r = e };
            P.Enqueue(node);
        }

        dfs(P.Peek(), 0);
        WriteLine(ans);
    }
    int ans = 0;
    void dfs(Node node, int depth)
    {
        if (node.l == null)
        {
            ans += depth * node.occurrence;
            return;
        }
        dfs(node.l, depth + 1);
        dfs(node.r, depth + 1);
    }
    class Node : IComparable<Node>
    {
        public int occurrence;
        public Node l, r;
        public Node(int occurrence)
        {
            this.occurrence = occurrence;
        }
        public int CompareTo(Node a)
        {
            return occurrence.CompareTo(a.occurrence);
        }
    }

}

/// <summary>
/// Original Author: 蟻本
/// </summary>
/// <typeparam name="T"></typeparam>
class PriorityQueue<T> where T : IComparable<T>
{
    List<T> heap;
    readonly int cmp;
    public PriorityQueue(int cmp = 1) { heap = new List<T>(); this.cmp = cmp; }
    public void Enqueue(T x)
    {
        heap.Add(x);
        int i = Count++;
        while (i > 0)
        {
            int p = (i - 1) >> 1;
            if (x.CompareTo(heap[p]) * cmp <= 0) break;
            heap[i] = heap[p]; i = p;
        }
        heap[i] = x;
    }
    public T Dequeue()
    {
        T ret = heap[0]; T x = heap[--Count];
        int i = 0;
        while ((i << 1) + 1 < Count)
        {
            int a = (i << 1) + 1; int b = (i << 1) + 2;
            if (b < Count && heap[a].CompareTo(heap[b]) * cmp < 0) a = b;
            if (x.CompareTo(heap[a]) * cmp >= 0) break;
            heap[i] = heap[a]; i = a;
        }
        heap[i] = x; heap.RemoveAt(Count);
        return ret;
    }
    public int Count { get; private set; }
    public bool Any() => Count > 0;
    public T Peek() => heap[0];
}

static class Ex
{
    public static void join<T>(this IEnumerable<T> values, string sep = " ") => WriteLine(string.Join(sep, values));
    public static string concat<T>(this IEnumerable<T> values) => string.Concat(values);
    public static string reverse(this string s) { var t = s.ToCharArray(); Array.Reverse(t); return t.concat(); }

    public static int lower_bound<T>(this IList<T> arr, T val) where T : IComparable<T>
    {
        int low = 0, high = arr.Count;
        int mid;
        while (low < high)
        {
            mid = ((high - low) >> 1) + low;
            if (arr[mid].CompareTo(val) < 0) low = mid + 1;
            else high = mid;
        }
        return low;
    }
    public static int upper_bound<T>(this IList<T> arr, T val) where T : IComparable<T>
    {
        int low = 0, high = arr.Count;
        int mid;
        while (low < high)
        {
            mid = ((high - low) >> 1) + low;
            if (arr[mid].CompareTo(val) <= 0) low = mid + 1;
            else high = mid;
        }
        return low;
    }
}

class Pair<T, U> : IComparable<Pair<T, U>> where T : IComparable<T> where U : IComparable<U>
{
    public T f; public U s;
    public Pair(T f, U s) { this.f = f; this.s = s; }
    public int CompareTo(Pair<T, U> a) => f.CompareTo(a.f) != 0 ? f.CompareTo(a.f) : s.CompareTo(a.s);
    public override string ToString() => $"{f} {s}";
}

class Scanner
{
    string[] s; int i;
    readonly char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan => ReadLine().Split();
    public int[] scanint => Array.ConvertAll(scan, int.Parse);
    public long[] scanlong => Array.ConvertAll(scan, long.Parse);
    public double[] scandouble => Array.ConvertAll(scan, double.Parse);
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint => int.Parse(next);
    public long nextlong => long.Parse(next);
    public double nextdouble => double.Parse(next);
}