
# 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

read = sys.stdin.buffer.read

readline = sys.stdin.buffer.readline

readlines = sys.stdin.buffer.readlines



import numpy as np



N = int(readline())

S = np.array(read().split(),np.int64)



def F(d):

    # 公差を固定

    L = S[:-d:d].cumsum()

    R = S[::-1][:-d:d].cumsum()

    if (N-1)%d == 0:

        n = (N-1)//d

        x = np.arange(1,n+1)

        bl = (x+x <= n+1)

        L = L[bl]; R = R[bl]

    return (L+R).max()



def G(n):

    # 項数n+1を固定

    D = (N-1-n)//n

    L = np.zeros(D+1,np.int64)

    R = np.zeros(D+1,np.int64)

    for i in range(1,n+1):

        L += S[:i*(D+1):i]

        R += S[::-1][:i*(D+1):i]

    ok = np.ones(D+1,np.bool)

    overlap = (np.arange(D+1) * (n+n) >= N-1)

    overlap[1:] &= ((N-1)%np.arange(1,D+1) == 0)

    x = L+R

    x[overlap] = 0

    return x.max()



L = int((N-1)**.5 + 10)

L = min(N-1,L)



x = max(F(n) for n in range(1,L+1))

y = max(G(n) for n in range(1,L+1))

answer = max(x,y)

print(answer)

# optimized version of the same code:

import sys

read = sys.stdin.buffer.read

readline = sys.stdin.buffer.readline

readlines = sys.stdin.buffer.readlines



import itertools



N = int(readline())

S = list(map(int,read().split()))



answer = 0

for d in range(1,N):

    n = (N-1)//d

    if (N-1)%d == 0:

        n = ((N-1)//d+1)//2

    if n <= 1:

        continue

    x = max(itertools.accumulate(x+y for x,y in zip(S[d:d*n:d],S[N-1-d:N-1-d*n:-d])))

    if answer < x:

        answer = x



print(answer)
import sys

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import numpy as np

N = int(readline())
S = np.array(read().split(), np.int64)


def F(d):
    # 公差を固定
    L = S[:-d:d].cumsum()
    R = S[::-1][:-d:d].cumsum()
    if (N - 1) % d == 0:
        n = (N - 1) // d
        x = np.arange(1, n + 1)
        bl = x + x <= n + 1
        L = L[bl]
        R = R[bl]
    return (L + R).max()


def G(n):
    # 項数n+1を固定
    D = (N - 1 - n) // n
    L = np.zeros(D + 1, np.int64)
    R = np.zeros(D + 1, np.int64)
    for i in range(1, n + 1):
        L += S[: i * (D + 1) : i]
        R += S[::-1][: i * (D + 1) : i]
    ok = np.ones(D + 1, np.bool)
    overlap = np.arange(D + 1) * (n + n) >= N - 1
    overlap[1:] &= (N - 1) % np.arange(1, D + 1) == 0
    x = L + R
    x[overlap] = 0
    return x.max()


L = int((N - 1) ** 0.5 + 10)
L = min(N - 1, L)
x = max(F(n) for n in range(1, L + 1))
y = max(G(n) for n in range(1, L + 1))
answer = max(x, y)
print(answer)

import sys

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

N = int(readline())
S = list(map(int, read().split()))
answer = 0
for d in range(1, N):
    n = (N - 1) // d
    if (N - 1) % d == 0:
        n = ((N - 1) // d + 1) // 2
    if n <= 1:
        continue
    x = max(
        itertools.accumulate(
            x + y for x, y in zip(S[d : d * n : d], S[N - 1 - d : N - 1 - d * n : -d])
        )
    )
    if answer < x:
        answer = x
print(answer)

-import numpy as np +import itertools -S = np.array(read().split(), np.int64) - - -def F(d): -    # 公差を固定 -    L = S[:-d:d].cumsum() -    R = S[::-1][:-d:d].cumsum() +S = list(map(int, read().split())) +answer = 0 +for d in range(1, N): +    n = (N - 1) // d -        n = (N - 1) // d -        x = np.arange(1, n + 1) -        bl = x + x <= n + 1 -        L = L[bl] -        R = R[bl] -    return (L + R).max() - - -def G(n): -    # 項数n+1を固定 -    D = (N - 1 - n) // n -    L = np.zeros(D + 1, np.int64) -    R = np.zeros(D + 1, np.int64) -    for i in range(1, n + 1): -        L += S[: i * (D + 1) : i] -        R += S[::-1][: i * (D + 1) : i] -    ok = np.ones(D + 1, np.bool) -    overlap = np.arange(D + 1) * (n + n) >= N - 1 -    overlap[1:] &= (N - 1) % np.arange(1, D + 1) == 0 -    x = L + R -    x[overlap] = 0 -    return x.max() - - -L = int((N - 1) ** 0.5 + 10) -L = min(N - 1, L) -x = max(F(n) for n in range(1, L + 1)) -y = max(G(n) for n in range(1, L + 1)) -answer = max(x, y) +        n = ((N - 1) // d + 1) // 2 +    if n <= 1: +        continue +    x = max( +        itertools.accumulate( +            x + y for x, y in zip(S[d : d * n : d], S[N - 1 - d : N - 1 - d * n : -d]) +        ) +    ) +    if answer < x: +        answer = x