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

Repeating cipher is used for strings. To encrypt the string $s=s_{1}s_{2} \dots s_{m}$ ($1 \le m \le 10$), 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" $\to$ "baa" $\to$ "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 $n$ ($1 \le n \le 55$) — 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

Difficulty: introductory

Starter code:

Solutions:
n = int(input())
s = input()
i = 0
d = 1
t = []
while i < n:
    t.append(s[i])
    i += d
    d += 1

print(''.join(t))


n=int(input())
s=input()
ans=""
i=0
ad=1
while i<n:
    ans+=s[i]
    i+=ad
    ad+=1
print(ans)

n=int(input())
a=input()
ans=''
now=0
dop=1
while now<=n:
    ans+=a[now]
    dop+=1
    now+=dop
print(ans)
    


n = int(input())
s = input()

i = 0
to_add = 1
while i < n:
    print(s[i], end='')
    i += to_add
    to_add += 1


n = int(input().strip())
s = str(input().strip())
c = 1
i = 0
while i < n:
    print(s[i],end='')
    i+=c
    c+=1


n=int(input())
s=str(input())
i=0
ans=""
count=1
while(i<n):
    ans+=s[i]
    i+=count
    count+=1
print(ans)



MOD = 10**9 + 7
I = lambda:list(map(int,input().split()))

n, = I()
s = input()
res = ''
i = 0
j = 2
while i < n:
    print(s[i], end='')
    i += j
    j += 1

def go():
    n = int(input())
    a = [i for i in input()]
    i = 0
    j = 1
    o = ''
    while i < n:
        o += a[i]
        i += j
        j += 1
    return o

print(go())


#      
import collections, atexit, math, sys, bisect 

sys.setrecursionlimit(1000000)
def getIntList():
    return list(map(int, input().split()))    

try :
    #raise ModuleNotFoundError
    import numpy
    def dprint(*args, **kwargs):
        #print(*args, **kwargs, file=sys.stderr)
        # in python 3.4 **kwargs is invalid???
        print(*args,  file=sys.stderr)
    dprint('debug mode')
except Exception:
    def dprint(*args, **kwargs):
        pass



inId = 0
outId = 0
if inId>0:
    dprint('use input', inId)
    sys.stdin = open('input'+ str(inId) + '.txt', 'r') #标准输出重定向至文件
if outId>0:
    dprint('use output', outId)
    sys.stdout = open('stdout'+ str(outId) + '.txt', 'w') #标准输出重定向至文件
    atexit.register(lambda :sys.stdout.close())     #idle 中不会执行 atexit
    
N, = getIntList()
#print(N)

s = input()

k = 0
r = ''
for i in range(1, 100000):
    if k>= N: break
    r += s[k]
    k+=i
    
print(r)





n = int(input())
s = input()
idx, cur = 0, 1
d = ''
while idx < n:
    d += s[idx]
    idx += cur
    cur += 1
print(d)


amount = int(input())
string = input()
answer = ''
counter = 1
i = 0
while i < len(string):
    answer += string[i]
    i += counter
    counter += 1
print(answer)

n = int(input()) 
# m = list(map(int, input().split()))
s = input()
c = 1
sol = ''
i = 0
while i < n:
    sol += s[i]
    i += c
    c += 1
print(sol)

#JMD
#Nagendra Jha-4096

 
import sys
import math

#import fractions
#import numpy
 
###File Operations###
fileoperation=0
if(fileoperation):
    orig_stdout = sys.stdout
    orig_stdin = sys.stdin
    inputfile = open('W:/Competitive Programming/input.txt', 'r')
    outputfile = open('W:/Competitive Programming/output.txt', 'w')
    sys.stdin = inputfile
    sys.stdout = outputfile

###Defines...###
mod=1000000007
 
###FUF's...###
def nospace(l):
    ans=''.join(str(i) for i in l)
    return ans
 
 
 
##### Main ####
t=1
for tt in range(t):
    n=int(input())
    s=str(input())
    c=1
    i=0
    ans=""
    while(i<n):
    	ans+=s[i]
    	i+=c
    	c+=1
    print(ans)
    #a=list(map(int,sys.stdin.readline().split(' ')))
    #n,k,s= map(int, sys.stdin.readline().split(' '))
    
    
#####File Operations#####
if(fileoperation):
    sys.stdout = orig_stdout
    sys.stdin = orig_stdin
    inputfile.close()
    outputfile.close()


n = int(input())
a = list(input())
ans = ''
pos = 0
count = 1
while pos < n:
    ans += a[pos]
    for i in range(count):
        pos += 1
    count += 1
print(ans)


n = int(input())
s = input()
count = 1
i = 0
ans = ""
for c in s:
	if(i == 0):
		ans += c
	i += 1
	if(i == count):
		i = 0
		count += 1
print(ans)

# alpha = "abcdefghijklmnopqrstuvwxyz"
t = 1
for test in range(t):
    # n,s = (map(int, input().split()))
    # a = list(map(int, input().split()))
    n = int(input())
    s = input()
    ind = 0
    cur = 1
    ans = []
    while ind<n:
        ans.append(s[ind])
        ind+=cur
        cur = cur+1
    print(*ans,sep="")



def read_nums():
    return [int(x) for x in input().split()]


def main():
    n, = read_nums()
    cipher = input()
    i = 0
    d = 1
    res = ''
    while i < n:
        res += cipher[i]
        i += d
        d += 1
    print(res)


def __starting_point():
    main()

__starting_point()

n = int(input())
s = input()
ans = ""
i = 0
y = 0
while i < n:
    ans += s[i]
    y += 1
    i += y
print(ans)

n = int(input())
string = input()

i = 1
cnt = 0
while cnt < n:
    print(string[cnt], end="")

    cnt += i
    i += 1


n = input()
enc = input()

i = 0
k = 0
dec = ''

while i < len(enc):
    dec += enc[i]
    k += 1
    i += k

print(dec)




n=int(input())
s=input()
itog=""
i=0
k=1
while i<len(s):
    itog+=(s[i])
    i+=k
    k+=1
print(itog)    
    


n=int(input())
a=input()
c=1
i=0
s=[]
while i<n:
    s.append(a[i])
    i+=c
    c+=1
print(*s,sep="")

n = int(input())
s = input().strip()
ans = ''
i = 0
k = 1
while (i < n):
    ans += s[i]
    i += k
    k += 1
print(ans)

n = int(input())
s = input()
d = ""
l = 0
for i in range(n):
    d = d + s[l]
    l = l + i + 1
    if l >= n:
        break

print(d)