Problem:
Score : 200 points

Problem Statement

We will call a string that can be obtained by concatenating two equal strings an even string.
For example, xyzxyz and aaaaaa are even, while ababab and xyzxy are not.

You are given an even string S consisting of lowercase English letters.
Find the length of the longest even string that can be obtained by deleting one or more characters from the end of S.
It is guaranteed that such a non-empty string exists for a given input.

Constraints

2 \leq |S| \leq 200

S is an even string consisting of lowercase English letters.

There exists a non-empty even string that can be obtained by deleting one or more characters from the end of S.

Input

Input is given from Standard Input in the following format:

S

Output

Print the length of the longest even string that can be obtained.

Sample Input 1

abaababaab

Sample Output 1

6

abaababaab itself is even, but we need to delete at least one character.

abaababaa is not even.

abaababa is not even.

abaabab is not even.

abaaba is even. Thus, we should print its length, 6.

Sample Input 2

xxxx

Sample Output 2

2

xxx is not even.

xx is even.

Sample Input 3

abcabcabcabc

Sample Output 3

6

The longest even string that can be obtained is abcabc, whose length is 6.

Sample Input 4

akasakaakasakasakaakas

Sample Output 4

14

The longest even string that can be obtained is akasakaakasaka, whose length is 14.

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
namespace AtCoder {
    class MainClass {

        string S;
        void Solve() {
            io.i(out S);

            for (; S.Length > 0; ) {
                S = S.Remove(S.Length - 1);
                if (S.Length % 2 != 0) continue;
                string f = S.Substring(0,S.Length/2);
                string b = S.Substring(S.Length / 2);
                if (f == b) break;
            }

            io.o(S.Length);

        }
        
        public static void Main(string[] args) { new MainClass().Stream(); }
        IO io = new IO();
        void Stream() { Solve(); io.writeFlush(); }

        class IO {
            string[] nextBuffer; int BufferCnt; char[] cs = new char[] { ' ' };
            StreamWriter sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            public IO() { nextBuffer = new string[0]; BufferCnt = 0; Console.SetOut(sw); }
            public string next() {
                if (BufferCnt < nextBuffer.Length) return nextBuffer[BufferCnt++];
                string st = Console.ReadLine();
                while (st == "") st = Console.ReadLine();
                nextBuffer = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
                BufferCnt = 0;
                return nextBuffer[BufferCnt++];
            }
            public char nextChar() { return char.Parse(next()); }
            public int nextInt() { return int.Parse(next()); }
            public long nextLong() { return long.Parse(next()); }
            public double nextDouble() { return double.Parse(next()); }
            public string[] array() { return Console.ReadLine().Split(' '); }
            public char[] arrayChar() { return Array.ConvertAll(array(), char.Parse); }
            public int[] arrayInt() { return Array.ConvertAll(array(), int.Parse); }
            public long[] arrayLong() { return Array.ConvertAll(array(), long.Parse); }
            public double[] arrayDouble() { return Array.ConvertAll(array(), double.Parse); }
            private bool typeEQ<T, U>() { return typeof(T).Equals(typeof(U)); }
            private T convertType<T, U>(U v) { return (T)Convert.ChangeType(v, typeof(T)); }
            private T suitType<T>(string s) {
                if (typeEQ<T, int>()) return convertType<T, int>(int.Parse(s));
                if (typeEQ<T, long>()) return convertType<T, long>(long.Parse(s));
                if (typeEQ<T, double>()) return convertType<T, double>(double.Parse(s));
                if (typeEQ<T, char>()) return convertType<T, char>(char.Parse(s));
                return convertType<T, string>(s);
            }
            public void i<T>(out T v) { v = suitType<T>(next()); }
            public void i<T, U>(out T v1, out U v2) {
                var a = array(); v1 = suitType<T>(a[0]); v2 = suitType<U>(a[1]);
            }
            public void i<T, U, V>(out T v1, out U v2, out V v3) {
                var a = array(); v1 = suitType<T>(a[0]); v2 = suitType<U>(a[1]);
                v3 = suitType<V>(a[2]);
            }
            public void i<T, U, V, W>(out T v1, out U v2, out V v3, out W v4) {
                var a = array(); v1 = suitType<T>(a[0]); v2 = suitType<U>(a[1]);
                v3 = suitType<V>(a[2]); v4 = suitType<W>(a[3]);
            }
            public void ini(out int[] a, int size) {
                a = new int[size]; for (int i = 0; i < size; i++) a[i] = nextInt();
            }
            public void ini(out int[] a1, out int[] a2, int size) {
                a1 = new int[size]; a2 = new int[size];
                for (int i = 0; i < size; i++) { a1[i] = nextInt(); a2[i] = nextInt(); }
            }
            public void ini(out string[] a, int size) {
                a = new string[size]; for (int i = 0; i < size; i++) a[i] = next();
            }
            public void inii(out int[] a, int size) {
                a = new int[size]; for (int i = 0; i < size; i++) a[i] = nextInt()-1;
            }
            public void o<T>(T v) { Console.WriteLine(v); }
            public void o<T>(params T[] a) { foreach (T v in a) Console.WriteLine(v); }
            public void o<T>(List<T> l) { foreach (T v in l) sw.WriteLine(v); }
            public void ol<T>(T v) { Console.Write(v + " "); }
            public void ol<T>(params T[] a) { foreach (T v in a) Console.Write(v + " "); Console.WriteLine(""); }
            public void YN(bool f) { Console.WriteLine(f ? "YES" : "NO"); }
            public void Yn(bool f) { Console.WriteLine(f ? "Yes" : "No"); }
            public void yn(bool f) { Console.WriteLine(f ? "yes" : "no"); }
            public void writeFlush() { Console.Out.Flush(); }
        }

        class Mathf {
            public int mod = 1000000007;//10^9+7
            public long Pow(long a, long b) {
                if (b == 0) return 1;
                if (b % 2 == 1) return (a % mod * Pow(a % mod, b - 1) % mod) % mod;
                else return Pow(a * a % mod, b / 2) % mod;
            }
            public long Fact(long n) { return n != 0 ? (n % mod * (Fact(n - 1) % mod) % mod) : 1; }
            public long C(long n, long r) {
                if (r == 0 || n == r) return 1;
                else return (Fact(n) % mod * Pow((Fact(n - r) % mod * Fact(r) % mod) % mod, mod - 2) % mod) % mod;
            }
            public long Sum(params long[] a) { return a.Aggregate((v, next) => (v % mod + next) % mod); }
            public int GCD(int a, int b) { if (a < b) Swap(ref a, ref b); return b == 0 ? a : GCD(b, a % b); }
            public int GCD(int[] array) { return array.Aggregate((v, next) => GCD(v, next)); }
            public void Swap<T>(ref T a, ref T b) { T tmp = a; a = b; b = tmp; }
            public T Max<T>(params T[] v) { return v.Max(); }
            public T Min<T>(params T[] v) { return v.Min(); }
        }
    }
    
    static class StringEX {
        public static string Reversed(this string s) { return string.Join("", s.Reverse()); }
        public static string Repeat(this string s, int n) { return string.Concat(Enumerable.Repeat(s, n).ToArray()); }
    }
}