
# 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:

from collections import deque

N = 3

m = {8: {7, 5}, 7: {8, 6, 4}, 6: {7, 3}, 5: {8, 4, 2}, 4: {7, 5, 3, 1}, 3: {6, 4, 0}, 2: {5, 1}, 1: {4, 2, 0},

     0: {3, 1}}

goal = 123456780

def g(i, j, a):

    t = a // (10 ** j) % 10

    return a - t * (10 ** j) + t * (10 ** i)

def solve():

    MAP = "".join(input().replace(" ", "") for _ in range(N))

    start = 8 - MAP.find("0")

    MAP = int(MAP)

    if MAP == goal:

        return 0

    dp = deque([(0, start, MAP)])

    LOG = {MAP}

    while dp:

        cnt, yx, M = dp.popleft()

        if M == goal:

            return cnt

        cnt += 1

        for nyx in m[yx]:

            CM = g(yx, nyx, M)

            if not CM in LOG:

                dp.append((cnt, nyx, CM))

                LOG.add(CM)

def MAIN():

    print((solve()))

MAIN()




# optimized version of the same code:

from collections import deque

N = 3

m = {8: {7, 5}, 7: {8, 6, 4}, 6: {7, 3}, 5: {8, 4, 2}, 4: {7, 5, 3, 1}, 3: {6, 4, 0}, 2: {5, 1}, 1: {4, 2, 0},

     0: {3, 1}}

goal = 123456780

def g(i, j, a):

    t = a // (10 ** j) % 10

    return a - t * (10 ** j) + t * (10 ** i)

def solve():

    MAP = "".join(input().replace(" ", "") for _ in range(N))

    zero = 8 - MAP.find("0")

    start = int(MAP)

    if start == goal:

        return 0

    dp = deque([(0, start, zero, 1), (0, goal, 0, 0)])

    TABLE = {start: (1, 0), goal: (0, 0)}

    while dp:

        cnt, M, yx, flg = dp.popleft()

        cnt += 1

        for nyx in m[yx]:

            key = g(yx, nyx, M)

            if key in TABLE:

                if TABLE[key][0] != flg:

                    return TABLE[key][1] + cnt

                continue

            TABLE[key] = (flg, cnt)

            dp.append((cnt, key, nyx, flg))

def MAIN():

    print((solve()))

MAIN()



from collections import deque

N = 3
m = {
    8: {7, 5},
    7: {8, 6, 4},
    6: {7, 3},
    5: {8, 4, 2},
    4: {7, 5, 3, 1},
    3: {6, 4, 0},
    2: {5, 1},
    1: {4, 2, 0},
    0: {3, 1},
}
goal = 123456780


def g(i, j, a):
    t = a // (10**j) % 10
    return a - t * (10**j) + t * (10**i)


def solve():
    MAP = "".join(input().replace(" ", "") for _ in range(N))
    start = 8 - MAP.find("0")
    MAP = int(MAP)
    if MAP == goal:
        return 0
    dp = deque([(0, start, MAP)])
    LOG = {MAP}
    while dp:
        cnt, yx, M = dp.popleft()
        if M == goal:
            return cnt
        cnt += 1
        for nyx in m[yx]:
            CM = g(yx, nyx, M)
            if not CM in LOG:
                dp.append((cnt, nyx, CM))
                LOG.add(CM)


def MAIN():
    print((solve()))


MAIN()

from collections import deque

N = 3
m = {
    8: {7, 5},
    7: {8, 6, 4},
    6: {7, 3},
    5: {8, 4, 2},
    4: {7, 5, 3, 1},
    3: {6, 4, 0},
    2: {5, 1},
    1: {4, 2, 0},
    0: {3, 1},
}
goal = 123456780


def g(i, j, a):
    t = a // (10**j) % 10
    return a - t * (10**j) + t * (10**i)


def solve():
    MAP = "".join(input().replace(" ", "") for _ in range(N))
    zero = 8 - MAP.find("0")
    start = int(MAP)
    if start == goal:
        return 0
    dp = deque([(0, start, zero, 1), (0, goal, 0, 0)])
    TABLE = {start: (1, 0), goal: (0, 0)}
    while dp:
        cnt, M, yx, flg = dp.popleft()
        cnt += 1
        for nyx in m[yx]:
            key = g(yx, nyx, M)
            if key in TABLE:
                if TABLE[key][0] != flg:
                    return TABLE[key][1] + cnt
                continue
            TABLE[key] = (flg, cnt)
            dp.append((cnt, key, nyx, flg))


def MAIN():
    print((solve()))


MAIN()

-    start = 8 - MAP.find("0") -    MAP = int(MAP) -    if MAP == goal: +    zero = 8 - MAP.find("0") +    start = int(MAP) +    if start == goal: -    dp = deque([(0, start, MAP)]) -    LOG = {MAP} +    dp = deque([(0, start, zero, 1), (0, goal, 0, 0)]) +    TABLE = {start: (1, 0), goal: (0, 0)} -        cnt, yx, M = dp.popleft() -        if M == goal: -            return cnt +        cnt, M, yx, flg = dp.popleft() -            CM = g(yx, nyx, M) -            if not CM in LOG: -                dp.append((cnt, nyx, CM)) -                LOG.add(CM) +            key = g(yx, nyx, M) +            if key in TABLE: +                if TABLE[key][0] != flg: +                    return TABLE[key][1] + cnt +                continue +            TABLE[key] = (flg, cnt) +            dp.append((cnt, key, nyx, flg))