
# 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 sys

import numpy as np



read = sys.stdin.buffer.read

readline = sys.stdin.buffer.readline

readlines = sys.stdin.buffer.readlines



def prime_table(N):

    is_prime = np.zeros(N, np.int64)

    is_prime[2:3] = 1

    is_prime[3::2] = 1

    for p in range(3, N, 2):

        if p * p >= N:

            break

        if is_prime[p]:

            is_prime[p * p::p + p] = 0

    return is_prime, np.where(is_prime)[0]



def main(N, primes):

    div = np.ones(N + 1, dtype=np.int64)

    for p in primes:

        for i in range(N // p + 1):

            div[p * i] += div[i]

    div *= np.arange(N + 1)

    return div.sum()



if sys.argv[-1] == 'ONLINE_JUDGE':

    import numba

    from numba.pycc import CC

    i8 = numba.int64

    cc = CC('my_module')



    def cc_export(f, signature):

        cc.export(f.__name__, signature)(f)

        return numba.njit(f)



    main = cc_export(main, (i8, i8[:]))

    cc.compile()



from my_module import main



N = int(read())

is_prime, primes = prime_table(N + 1)

print((main(N, primes)))

# optimized version of the same code:

N = int(eval(input()))



def f(x):

  return x * (x+1) // 2



ans = 0

for x in range(1, N+1):

  if x * x > N:

    break

  # x = y

  ans += x * x

  # x < y の 2 倍

  y_high = N//x

  ans += 2 * x * (f(y_high) - f(x))



print(ans)
import sys
import numpy as np

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


def prime_table(N):
    is_prime = np.zeros(N, np.int64)
    is_prime[2:3] = 1
    is_prime[3::2] = 1
    for p in range(3, N, 2):
        if p * p >= N:
            break
        if is_prime[p]:
            is_prime[p * p :: p + p] = 0
    return is_prime, np.where(is_prime)[0]


def main(N, primes):
    div = np.ones(N + 1, dtype=np.int64)
    for p in primes:
        for i in range(N // p + 1):
            div[p * i] += div[i]
    div *= np.arange(N + 1)
    return div.sum()


if sys.argv[-1] == "ONLINE_JUDGE":
    import numba
    from numba.pycc import CC

    i8 = numba.int64
    cc = CC("my_module")

    def cc_export(f, signature):
        cc.export(f.__name__, signature)(f)
        return numba.njit(f)

    main = cc_export(main, (i8, i8[:]))
    cc.compile()
from my_module import main

N = int(read())
is_prime, primes = prime_table(N + 1)
print((main(N, primes)))

N = int(eval(input()))


def f(x):
    return x * (x + 1) // 2


ans = 0
for x in range(1, N + 1):
    if x * x > N:
        break
    # x = y
    ans += x * x
    # x < y の 2 倍
    y_high = N // x
    ans += 2 * x * (f(y_high) - f(x))
print(ans)

-import sys -import numpy as np - -read = sys.stdin.buffer.read -readline = sys.stdin.buffer.readline -readlines = sys.stdin.buffer.readlines +N = int(eval(input())) -def prime_table(N): -    is_prime = np.zeros(N, np.int64) -    is_prime[2:3] = 1 -    is_prime[3::2] = 1 -    for p in range(3, N, 2): -        if p * p >= N: -            break -        if is_prime[p]: -            is_prime[p * p :: p + p] = 0 -    return is_prime, np.where(is_prime)[0] +def f(x): +    return x * (x + 1) // 2 -def main(N, primes): -    div = np.ones(N + 1, dtype=np.int64) -    for p in primes: -        for i in range(N // p + 1): -            div[p * i] += div[i] -    div *= np.arange(N + 1) -    return div.sum() - - -if sys.argv[-1] == "ONLINE_JUDGE": -    import numba -    from numba.pycc import CC - -    i8 = numba.int64 -    cc = CC("my_module") - -    def cc_export(f, signature): -        cc.export(f.__name__, signature)(f) -        return numba.njit(f) - -    main = cc_export(main, (i8, i8[:])) -    cc.compile() -from my_module import main - -N = int(read()) -is_prime, primes = prime_table(N + 1) -print((main(N, primes))) +ans = 0 +for x in range(1, N + 1): +    if x * x > N: +        break +    # x = y +    ans += x * x +    # x < y の 2 倍 +    y_high = N // x +    ans += 2 * x * (f(y_high) - f(x)) +print(ans)