
# slower version:

s = input()
for i in range(len(s)):
  if i%2 == 0:
    print(s[i], end = '')


# optimized version of the same code:

s = input()
ans = ''
for i in range(len(s)):
  if i % 2 == 0:
    ans += s[i]
print(ans)



# slower version:

import numpy as np



n = int(eval(input()))

a_list = list(map(int, input().split()))



alice_point = 0

bob_point = 0

for i in range(n):

    argmax_a = np.argmax(a_list)

    max_a = np.max(a_list)

    if i % 2 == 0: # If Alice takes a card

        alice_point += max_a

    else: # If Bob takes a card

        bob_point += max_a

    del a_list[argmax_a] # No confidence -> Review how to delete list element!



print((alice_point - bob_point))

# optimized version of the same code:

n = int(eval(input()))

a_list = list(map(int, input().split()))

a_list = sorted(a_list, reverse=True)



alice_point = 0

bob_point = 0

for i in range(n):

    if i % 2 == 0:

        alice_point += a_list[i]

    else:

        bob_point += a_list[i]



print((alice_point - bob_point))
import numpy as np

n = int(eval(input()))
a_list = list(map(int, input().split()))
alice_point = 0
bob_point = 0
for i in range(n):
    argmax_a = np.argmax(a_list)
    max_a = np.max(a_list)
    if i % 2 == 0:  # If Alice takes a card
        alice_point += max_a
    else:  # If Bob takes a card
        bob_point += max_a
    del a_list[argmax_a]  # No confidence -> Review how to delete list element!
print((alice_point - bob_point))

n = int(eval(input()))
a_list = list(map(int, input().split()))
a_list = sorted(a_list, reverse=True)
alice_point = 0
bob_point = 0
for i in range(n):
    if i % 2 == 0:
        alice_point += a_list[i]
    else:
        bob_point += a_list[i]
print((alice_point - bob_point))

-import numpy as np - +a_list = sorted(a_list, reverse=True) -    argmax_a = np.argmax(a_list) -    max_a = np.max(a_list) -    if i % 2 == 0:  # If Alice takes a card -        alice_point += max_a -    else:  # If Bob takes a card -        bob_point += max_a -    del a_list[argmax_a]  # No confidence -> Review how to delete list element! +    if i % 2 == 0: +        alice_point += a_list[i] +    else: +        bob_point += a_list[i]