Problem: Polycarp loves ciphers. He has invented his own cipher called repeating.

Repeating cipher is used for strings. To encrypt the string s=s_{1}s_{2} ... s_{m} (1 ≤ m ≤ 10), Polycarp uses the following algorithm:

  * he writes down s_1 ones, 
  * he writes down s_2 twice, 
  * he writes down s_3 three times, 
  * ... 
  * he writes down s_m m times. 



For example, if s="bab" the process is: "b" → "baa" → "baabbb". So the encrypted s="bab" is "baabbb".

Given string t — the result of encryption of some string s. Your task is to decrypt it, i. e. find the string s.

Input

The first line contains integer n (1 ≤ n ≤ 55) — the length of the encrypted string. The second line of the input contains t — the result of encryption of some string s. It contains only lowercase Latin letters. The length of t is exactly n.

It is guaranteed that the answer to the test exists.

Output

Print such string s that after encryption it equals t.

Examples

Input


6
baabbb


Output


bab

Input


10
ooopppssss


Output


oops

Input


1
z


Output


z

Solution (in PYTHON):

Solution:

from __future__ import division
from fractions import Fraction
import math
import random,bisect
import sys
#import os
#import random
#import re
from sys import stdin, stdout
#from collections import Counter,deque,OrderedDict,defaultdict
#from itertools import permutations,ansduct,combinations
#from heapq import heapify,heappush,heappop,heappushpop,heapify,heapreplace,nlargest,nsmallest
#import numpy as np
#from operator import mul

MOD=10**6+3
INF=float('+inf')

def si():
	return str(stdin.readline())
def ii():
    return int(raw_input())
def mi():
    return map(int, raw_input().split())
def li():
    return [int(i) for i in raw_input().split()]
def debug(x):
	return stdout.write(str(x))
def limul(list):
	return eval('*'.join(str(item) for item in list))

"-----------------------------------------------"

def main():
	n=ii()
	arr=raw_input()
	ans=[]
	index=[0,2,5,9,14,20,27,35,44,54]
	l=len(index)
	ans_index=[]
	for i in range(l):
		if index[i]==n-1:
			answer=i
			break
	for i in range(answer+1):
		ans.append(arr[index[i]])
	print ''.join(str(e) for e in ans)



















main()