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 PYTHON3):

Solution:
import sys
import math

#to read string
get_string = lambda: sys.stdin.readline().strip()
#to read list of integers
get_list = lambda: list( map(int,sys.stdin.readline().strip().split()) )
#to read non spaced string and elements are integers to list of int
get_intList_from_str = lambda: list(map(int,list(sys.stdin.readline().strip())))
#to read non spaced string and elements are character to list of character
get_strList_from_str = lambda: list(sys.stdin.readline().strip())
#to read integers
get_int = lambda: int(sys.stdin.readline().strip())
#to print faster
pt = lambda x: sys.stdout.write(str(x))

#--------------------------------WhiteHat010--------------------------------------#

n = get_int()
string = get_string()

len_actual_str = math.floor( ( -1 + math.sqrt(1+8*n) )//2 )

result = ""
index = 0
incrementer = 1
for i in range(len_actual_str):
    result += string[index]
    index += incrementer
    incrementer += 1
print(result)