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:

def get_n(m):
    result = -1
    res_lis = []
    z = 0
    for i in range(m):
        if (i+1)*(i+2) == 2*m:
            result = i+1
    for i in range(result):
        z+=i
        res_lis.append(z)
    return result,res_lis

def get_result(str,res_lis):
    z = 0
    result = ''
    for i in res_lis:
        result=result+str[i]
    print result
m = int(raw_input())
str = raw_input()
n,res_lis = get_n(m)
get_result(str,res_lis)