
# 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

input = sys.stdin.readline

from collections import deque

N = int(eval(input()))

X = [[] for i in range(N)]

for i in range(N-1):

    x, y = list(map(int, input().split()))

    X[x-1].append(y-1)

    X[y-1].append(x-1)

i0 = min([i for i in range(N) if len(X[i]) == 1])



P = [-1] * N

Q = deque([i0])

R = []

while Q:

    i = deque.popleft(Q)

    R.append(i)

    for a in X[i]:

        if a != P[i]:

            P[a] = i

            X[a].remove(i)

            deque.append(Q, a)



mod = 10 ** 9 + 7

inv2 = (mod + 1) // 2

A = [1] * N

for i in R[::-1]:

    s = 0

    for j in X[i]:

        A[i] += A[j]



ans = 0

for i in range(N):

    s = pow(inv2, N - A[i], mod)

    t = 1 + (1-pow(inv2, N - A[i], mod)) * pow(2, N - A[i], mod)

    for j in X[i]:

        s = (s * pow(inv2, A[j], mod)) % mod

        t = (t + (1-pow(inv2, A[j], mod)) * pow(2, A[j], mod)) % mod

    ans = (ans + 1 - s * t) % mod



print((ans * inv2 % mod))

# optimized version of the same code:

import sys

input = sys.stdin.readline

from collections import deque

N = int(eval(input()))

X = [[] for i in range(N)]

for i in range(N-1):

    x, y = list(map(int, input().split()))

    X[x-1].append(y-1)

    X[y-1].append(x-1)

i0 = min([i for i in range(N) if len(X[i]) == 1])



P = [-1] * N

Q = deque([i0])

R = []

while Q:

    i = deque.popleft(Q)

    R.append(i)

    for a in X[i]:

        if a != P[i]:

            P[a] = i

            X[a].remove(i)

            deque.append(Q, a)



mod = 10 ** 9 + 7

pow2 = [1]

for i in range(N + 10):

    pow2.append(pow2[-1] * 2 % mod)

inv2 = (mod + 1) // 2



invpow2 = [pow(pow2[-1], mod-2, mod)]

for i in range(N + 10)[::-1]:

    invpow2.append(invpow2[-1] * 2 % mod)

invpow2 = invpow2[::-1]



A = [1] * N

for i in R[::-1]:

    s = 0

    for j in X[i]:

        A[i] += A[j]



ans = 0

for i in range(N):

    s = pow(inv2, N - A[i], mod)

    t = 1 + (1-invpow2[N-A[i]]) * pow2[N-A[i]]

    for j in X[i]:

        s = (s * invpow2[A[j]]) % mod

        t = (t + (1-invpow2[A[j]]) * pow2[A[j]]) % mod

    ans = (ans + 1 - s * t) % mod



print((ans * inv2 % mod))
import sys

input = sys.stdin.readline
from collections import deque

N = int(eval(input()))
X = [[] for i in range(N)]
for i in range(N - 1):
    x, y = list(map(int, input().split()))
    X[x - 1].append(y - 1)
    X[y - 1].append(x - 1)
i0 = min([i for i in range(N) if len(X[i]) == 1])
P = [-1] * N
Q = deque([i0])
R = []
while Q:
    i = deque.popleft(Q)
    R.append(i)
    for a in X[i]:
        if a != P[i]:
            P[a] = i
            X[a].remove(i)
            deque.append(Q, a)
mod = 10**9 + 7
inv2 = (mod + 1) // 2
A = [1] * N
for i in R[::-1]:
    s = 0
    for j in X[i]:
        A[i] += A[j]
ans = 0
for i in range(N):
    s = pow(inv2, N - A[i], mod)
    t = 1 + (1 - pow(inv2, N - A[i], mod)) * pow(2, N - A[i], mod)
    for j in X[i]:
        s = (s * pow(inv2, A[j], mod)) % mod
        t = (t + (1 - pow(inv2, A[j], mod)) * pow(2, A[j], mod)) % mod
    ans = (ans + 1 - s * t) % mod
print((ans * inv2 % mod))

import sys

input = sys.stdin.readline
from collections import deque

N = int(eval(input()))
X = [[] for i in range(N)]
for i in range(N - 1):
    x, y = list(map(int, input().split()))
    X[x - 1].append(y - 1)
    X[y - 1].append(x - 1)
i0 = min([i for i in range(N) if len(X[i]) == 1])
P = [-1] * N
Q = deque([i0])
R = []
while Q:
    i = deque.popleft(Q)
    R.append(i)
    for a in X[i]:
        if a != P[i]:
            P[a] = i
            X[a].remove(i)
            deque.append(Q, a)
mod = 10**9 + 7
pow2 = [1]
for i in range(N + 10):
    pow2.append(pow2[-1] * 2 % mod)
inv2 = (mod + 1) // 2
invpow2 = [pow(pow2[-1], mod - 2, mod)]
for i in range(N + 10)[::-1]:
    invpow2.append(invpow2[-1] * 2 % mod)
invpow2 = invpow2[::-1]
A = [1] * N
for i in R[::-1]:
    s = 0
    for j in X[i]:
        A[i] += A[j]
ans = 0
for i in range(N):
    s = pow(inv2, N - A[i], mod)
    t = 1 + (1 - invpow2[N - A[i]]) * pow2[N - A[i]]
    for j in X[i]:
        s = (s * invpow2[A[j]]) % mod
        t = (t + (1 - invpow2[A[j]]) * pow2[A[j]]) % mod
    ans = (ans + 1 - s * t) % mod
print((ans * inv2 % mod))

+pow2 = [1] +for i in range(N + 10): +    pow2.append(pow2[-1] * 2 % mod) +invpow2 = [pow(pow2[-1], mod - 2, mod)] +for i in range(N + 10)[::-1]: +    invpow2.append(invpow2[-1] * 2 % mod) +invpow2 = invpow2[::-1] -    t = 1 + (1 - pow(inv2, N - A[i], mod)) * pow(2, N - A[i], mod) +    t = 1 + (1 - invpow2[N - A[i]]) * pow2[N - A[i]] -        s = (s * pow(inv2, A[j], mod)) % mod -        t = (t + (1 - pow(inv2, A[j], mod)) * pow(2, A[j], mod)) % mod +        s = (s * invpow2[A[j]]) % mod +        t = (t + (1 - invpow2[A[j]]) * pow2[A[j]]) % mod