
# 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:

def popcount(x):

    x = x - ((x >> 1) & 0x55555555)

    x = (x & 0x33333333) + ((x >> 2) & 0x33333333)

    x = (x + (x >> 4)) & 0x0f0f0f0f

    x = x + (x >> 8)

    x = x + (x >> 16)

    return x & 0x0000007f



cmb=[[0 for i in range(51)] for j in range(51)]

cmb[0][0]=1

for i in range(51):

    for j in range(51):

        if i!=50 and j!=50:

            cmb[i+1][j+1]+=cmb[i][j]

        if i!=50:

            cmb[i+1][j]+=cmb[i][j]



for i in range(1,51):

    for j in range(2,51):

        cmb[i][j]+=cmb[i][j-1]



N,K,T,S=list(map(int,input().split()))

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



must0=[i for i in range(18) if S>>i &1==0]

must1=[i for i in range(18) if T>>i &1==1]



A=[]

for val in a:

    check=True

    for j in must0:

        check=check&(val>>j &1==0)

    for j in must1:

        check=check&(val>>j &1==1)

    if check:

        A.append(val)



if not A:

    print((0))

    exit()



bit=[]

for i in range(18):

    if i not in must0 and i not in must1:

        bit.append(i)



for i in range(len(A)):

    temp=0

    for j in range(len(bit)):

        temp+=(A[i]>>bit[j] &1==1)*2**j

    A[i]=temp



ans=0

n=len(bit)

data=[0]*(2**n)

for i in range(2**n):

    t=set([])

    for a in A:

        data[a&i]+=1

        t.add(a&i)

    temp=0

    for val in t:

        temp+=cmb[data[val]][min(K,data[val])]

    ans+=temp*(-1)**popcount(i)

    for val in t:

        data[val]=0



print(ans)


# optimized version of the same code:

def popcount(x):

    x = x - ((x >> 1) & 0x55555555)

    x = (x & 0x33333333) + ((x >> 2) & 0x33333333)

    x = (x + (x >> 4)) & 0x0f0f0f0f

    x = x + (x >> 8)

    x = x + (x >> 16)

    return x & 0x0000007f



cmb=[[0 for i in range(51)] for j in range(51)]

cmb[0][0]=1

for i in range(51):

    for j in range(51):

        if i!=50:

            cmb[i+1][j]+=cmb[i][j]

        if j!=50 and i!=50:

            cmb[i+1][j+1]+=cmb[i][j]





for i in range(1,51):

    for j in range(2,51):

        cmb[i][j]+=cmb[i][j-1]



import random

N,K,T,S=list(map(int,input().split()))

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



must0=[i for i in range(18) if S>>i &1==0]

must1=[i for i in range(18) if T>>i &1==1]



A=[]

for val in a:

    check=True

    for j in must0:

        check=check&(val>>j &1==0)

    for j in must1:

        check=check&(val>>j &1==1)

    if check:

        A.append(val)



if not A:

    print((0))

    exit()



bit=[]

for i in range(18):

    if i not in must0 and i not in must1:

        bit.append(i)



for i in range(len(A)):

    temp=0

    for j in range(len(bit)):

        temp+=(A[i]>>bit[j] &1==1)*2**j

    A[i]=temp



ans=0

n=len(bit)

data=[0]*(2**n)

pc=[popcount(i) for i in range(2**n)]

for i in range(2**n):

    for a in A:

        data[a&i]+=1

    for a in A:

        if data[a&i]:

            ans+=cmb[data[a&i]][min(K,data[a&i])]*(-1)**pc[i]

            data[a&i]=0



print(ans)
def popcount(x):
    x = x - ((x >> 1) & 0x55555555)
    x = (x & 0x33333333) + ((x >> 2) & 0x33333333)
    x = (x + (x >> 4)) & 0x0F0F0F0F
    x = x + (x >> 8)
    x = x + (x >> 16)
    return x & 0x0000007F


cmb = [[0 for i in range(51)] for j in range(51)]
cmb[0][0] = 1
for i in range(51):
    for j in range(51):
        if i != 50 and j != 50:
            cmb[i + 1][j + 1] += cmb[i][j]
        if i != 50:
            cmb[i + 1][j] += cmb[i][j]
for i in range(1, 51):
    for j in range(2, 51):
        cmb[i][j] += cmb[i][j - 1]
N, K, T, S = list(map(int, input().split()))
a = list(map(int, input().split()))
must0 = [i for i in range(18) if S >> i & 1 == 0]
must1 = [i for i in range(18) if T >> i & 1 == 1]
A = []
for val in a:
    check = True
    for j in must0:
        check = check & (val >> j & 1 == 0)
    for j in must1:
        check = check & (val >> j & 1 == 1)
    if check:
        A.append(val)
if not A:
    print((0))
    exit()
bit = []
for i in range(18):
    if i not in must0 and i not in must1:
        bit.append(i)
for i in range(len(A)):
    temp = 0
    for j in range(len(bit)):
        temp += (A[i] >> bit[j] & 1 == 1) * 2**j
    A[i] = temp
ans = 0
n = len(bit)
data = [0] * (2**n)
for i in range(2**n):
    t = set([])
    for a in A:
        data[a & i] += 1
        t.add(a & i)
    temp = 0
    for val in t:
        temp += cmb[data[val]][min(K, data[val])]
    ans += temp * (-1) ** popcount(i)
    for val in t:
        data[val] = 0
print(ans)

def popcount(x):
    x = x - ((x >> 1) & 0x55555555)
    x = (x & 0x33333333) + ((x >> 2) & 0x33333333)
    x = (x + (x >> 4)) & 0x0F0F0F0F
    x = x + (x >> 8)
    x = x + (x >> 16)
    return x & 0x0000007F


cmb = [[0 for i in range(51)] for j in range(51)]
cmb[0][0] = 1
for i in range(51):
    for j in range(51):
        if i != 50:
            cmb[i + 1][j] += cmb[i][j]
        if j != 50 and i != 50:
            cmb[i + 1][j + 1] += cmb[i][j]
for i in range(1, 51):
    for j in range(2, 51):
        cmb[i][j] += cmb[i][j - 1]
import random

N, K, T, S = list(map(int, input().split()))
a = list(map(int, input().split()))
must0 = [i for i in range(18) if S >> i & 1 == 0]
must1 = [i for i in range(18) if T >> i & 1 == 1]
A = []
for val in a:
    check = True
    for j in must0:
        check = check & (val >> j & 1 == 0)
    for j in must1:
        check = check & (val >> j & 1 == 1)
    if check:
        A.append(val)
if not A:
    print((0))
    exit()
bit = []
for i in range(18):
    if i not in must0 and i not in must1:
        bit.append(i)
for i in range(len(A)):
    temp = 0
    for j in range(len(bit)):
        temp += (A[i] >> bit[j] & 1 == 1) * 2**j
    A[i] = temp
ans = 0
n = len(bit)
data = [0] * (2**n)
pc = [popcount(i) for i in range(2**n)]
for i in range(2**n):
    for a in A:
        data[a & i] += 1
    for a in A:
        if data[a & i]:
            ans += cmb[data[a & i]][min(K, data[a & i])] * (-1) ** pc[i]
            data[a & i] = 0
print(ans)

-        if i != 50 and j != 50: -            cmb[i + 1][j + 1] += cmb[i][j] +        if j != 50 and i != 50: +            cmb[i + 1][j + 1] += cmb[i][j] +import random + +pc = [popcount(i) for i in range(2**n)] -    t = set([]) -        t.add(a & i) -    temp = 0 -    for val in t: -        temp += cmb[data[val]][min(K, data[val])] -    ans += temp * (-1) ** popcount(i) -    for val in t: -        data[val] = 0 +    for a in A: +        if data[a & i]: +            ans += cmb[data[a & i]][min(K, data[a & i])] * (-1) ** pc[i] +            data[a & i] = 0