output_description: Print the length of the longest even string that can be obtained.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S
attempt: import sys, re
  from collections import deque, defaultdict, Counter
  from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
  from itertools import accumulate, permutations, combinations, product, groupby
  from operator import itemgetter, mul
  from copy import deepcopy
  from string import ascii_lowercase, ascii_uppercase, digits
  from bisect import bisect, bisect_left
  from fractions import gcd
  from heapq import heappush, heappop
  from functools import reduce
  def input(): return sys.stdin.readline().strip()
  def INT(): return int(input())
  def MAP(): return map(int, input().split())
  def LIST(): return list(map(int, input().split()))
  def ZIP(n): return zip(*(MAP() for _ in range(n)))
  sys.setrecursionlimit(10 ** 9)
  INF = float('inf')
  mod = 10 ** 9 + 7
   
  S = input()
  
  for i in range(1, len(S)):
  	T = S[:-2*i]
  	if T[:len(T)//2] == T[len(T//2:)]:
  		print(len(T))
  		break
problem_description: 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.
samples: [{"input": "abaababaab", "output": "6\n    \n\n  * `abaababaab` itself is even, but we need to delete at least one character.\n  * `abaababaa` is not even.\n  * `abaababa` is not even.\n  * `abaabab` is not even.\n  * `abaaba` is even. Thus, we should print its length, 6.\n\n* * *"}, {"input": "xxxx", "output": "2\n    \n\n  * `xxx` is not even.\n  * `xx` is even.\n\n* * *"}, {"input": "abcabcabcabc", "output": "6\n    \n\nThe longest even string that can be obtained is `abcabc`, whose length is 6.\n\n* * *"}, {"input": "akasakaakasakasakaakas", "output": "14\n    \n\nThe longest even string that can be obtained is `akasakaakasaka`, whose length\nis 14."}]