
# 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 scipy.sparse.csgraph import dijkstra

import numpy as np



"""

最小カット

"""



N = int(eval(input()))

start = 0

goal = N+1



A = [0] + [int(x) for x in input().split()]



INF = 10 ** 12

graph = np.zeros((N+2,N+2),dtype=np.int64)

for i,a in enumerate(A[1:],1):

    if a >= 0:

        graph[start,i] = a

    else:

        graph[i,goal] = -a

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

    for j in range(2*i,N+1,i):

        if A[i] < 0 and A[j] > 0:

            graph[j][i] = INF



def max_flow(graph):

    flow = 0

    while True:

        dist,pred = dijkstra(graph, indices = start, return_predecessors = True, unweighted = True)

        if dist[goal] == np.inf:

            return flow

        path = []

        v = goal

        while True:

            path.append((pred[v],v))

            v = pred[v]

            if v == start:

                break

        add_flow = min(graph[x][y] for x,y in path)

        for x,y in path:

            graph[x][y] -= add_flow

            graph[y][x] += add_flow

        flow += add_flow



answer = sum(x for x in A if x > 0) - max_flow(graph)

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



from collections import deque



N,*A = list(map(int,read().split()))



class Dinic:

    def __init__(self, N, source, sink):

        self.N = N

        self.G = [[] for _ in range(N)]

        self.source = source

        self.sink = sink



    def add_edge(self, fr, to, cap):

        n1 = len(self.G[fr])

        n2 = len(self.G[to])

        self.G[fr].append([to, cap, n2])

        self.G[to].append([fr, 0, n1]) # 逆辺を cap 0 で追加

        

    def add_edge_undirected(self, fr, to, cap):

        n1 = len(self.G[fr])

        n2 = len(self.G[to])

        self.G[fr].append([to, cap, n2])

        self.G[to].append([fr, cap, n1])

        

    def bfs(self):

        level = [0] * self.N

        G = self.G; source = self.source; sink = self.sink

        q = deque([source])

        level[source] = 1

        pop = q.popleft; append = q.append

        while q:

            v = pop()

            lv = level[v] + 1

            for to, cap, rev in G[v]:

                if not cap:

                    continue

                if level[to]:

                    continue

                level[to] = lv

                if to == sink:

                    self.level = level

                    return

                append(to)

        self.level = level

        

    def dfs(self,v,f):

        if v == self.sink:

            return f

        G = self.G

        prog = self.progress

        level = self.level

        lv = level[v]

        E = G[v]

        for i in range(prog[v],len(E)):

            to, cap, rev = E[i]

            prog[v] = i

            if not cap:

                continue

            if level[to] <= lv:

                continue

            x = f if f < cap else cap

            ff = self.dfs(to, x)

            if ff:

                E[i][1] -= ff

                G[to][rev][1] += ff

                return ff

        return 0

    

    def max_flow(self):

        INF = 10**18

        flow = 0

        while True:

            self.bfs()

            if not self.level[self.sink]:

                return flow

            self.progress = [0] * self.N

            while True:

                f = self.dfs(self.source, INF)

                if not f:

                    break

                flow += f

        return flow



source = 0; sink = N+1; INF = 10 ** 18

dinic = Dinic(N+2,source,sink)

add = dinic.add_edge



for i,x in enumerate(A,1):

    if x < 0:

        # source側：割るものを表現。sink側にうつすときにカット-xが必要。

        add(source,i,-x)

    else:

        # sink側：割らないものを表現。source側にうつすときにカットxが必要。

        add(i,sink,x)



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

    for j in range(i+i,N+1,i):

        # iを割るならjも割る。iを割ってjを割らないのは禁止

        # iがsourceでjがsinkなのは禁止

        add(i,j,INF)



f = dinic.max_flow()

x = sum(x for x in A if x >= 0)

answer = x - f



print(answer)
import sys

input = sys.stdin.readline
from scipy.sparse.csgraph import dijkstra
import numpy as np

"""
最小カット
"""
N = int(eval(input()))
start = 0
goal = N + 1
A = [0] + [int(x) for x in input().split()]
INF = 10**12
graph = np.zeros((N + 2, N + 2), dtype=np.int64)
for i, a in enumerate(A[1:], 1):
    if a >= 0:
        graph[start, i] = a
    else:
        graph[i, goal] = -a
for i in range(1, N + 1):
    for j in range(2 * i, N + 1, i):
        if A[i] < 0 and A[j] > 0:
            graph[j][i] = INF


def max_flow(graph):
    flow = 0
    while True:
        dist, pred = dijkstra(
            graph, indices=start, return_predecessors=True, unweighted=True
        )
        if dist[goal] == np.inf:
            return flow
        path = []
        v = goal
        while True:
            path.append((pred[v], v))
            v = pred[v]
            if v == start:
                break
        add_flow = min(graph[x][y] for x, y in path)
        for x, y in path:
            graph[x][y] -= add_flow
            graph[y][x] += add_flow
        flow += add_flow


answer = sum(x for x in A if x > 0) - max_flow(graph)
print(answer)

import sys

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
from collections import deque

N, *A = list(map(int, read().split()))


class Dinic:
    def __init__(self, N, source, sink):
        self.N = N
        self.G = [[] for _ in range(N)]
        self.source = source
        self.sink = sink

    def add_edge(self, fr, to, cap):
        n1 = len(self.G[fr])
        n2 = len(self.G[to])
        self.G[fr].append([to, cap, n2])
        self.G[to].append([fr, 0, n1])  # 逆辺を cap 0 で追加

    def add_edge_undirected(self, fr, to, cap):
        n1 = len(self.G[fr])
        n2 = len(self.G[to])
        self.G[fr].append([to, cap, n2])
        self.G[to].append([fr, cap, n1])

    def bfs(self):
        level = [0] * self.N
        G = self.G
        source = self.source
        sink = self.sink
        q = deque([source])
        level[source] = 1
        pop = q.popleft
        append = q.append
        while q:
            v = pop()
            lv = level[v] + 1
            for to, cap, rev in G[v]:
                if not cap:
                    continue
                if level[to]:
                    continue
                level[to] = lv
                if to == sink:
                    self.level = level
                    return
                append(to)
        self.level = level

    def dfs(self, v, f):
        if v == self.sink:
            return f
        G = self.G
        prog = self.progress
        level = self.level
        lv = level[v]
        E = G[v]
        for i in range(prog[v], len(E)):
            to, cap, rev = E[i]
            prog[v] = i
            if not cap:
                continue
            if level[to] <= lv:
                continue
            x = f if f < cap else cap
            ff = self.dfs(to, x)
            if ff:
                E[i][1] -= ff
                G[to][rev][1] += ff
                return ff
        return 0

    def max_flow(self):
        INF = 10**18
        flow = 0
        while True:
            self.bfs()
            if not self.level[self.sink]:
                return flow
            self.progress = [0] * self.N
            while True:
                f = self.dfs(self.source, INF)
                if not f:
                    break
                flow += f
        return flow


source = 0
sink = N + 1
INF = 10**18
dinic = Dinic(N + 2, source, sink)
add = dinic.add_edge
for i, x in enumerate(A, 1):
    if x < 0:
        # source側：割るものを表現。sink側にうつすときにカット-xが必要。
        add(source, i, -x)
    else:
        # sink側：割らないものを表現。source側にうつすときにカットxが必要。
        add(i, sink, x)
for i in range(1, N + 1):
    for j in range(i + i, N + 1, i):
        # iを割るならjも割る。iを割ってjを割らないのは禁止
        # iがsourceでjがsinkなのは禁止
        add(i, j, INF)
f = dinic.max_flow()
x = sum(x for x in A if x >= 0)
answer = x - f
print(answer)

-input = sys.stdin.readline -from scipy.sparse.csgraph import dijkstra -import numpy as np +read = sys.stdin.buffer.read +readline = sys.stdin.buffer.readline +readlines = sys.stdin.buffer.readlines +from collections import deque -""" -最小カット -""" -N = int(eval(input())) -start = 0 -goal = N + 1 -A = [0] + [int(x) for x in input().split()] -INF = 10**12 -graph = np.zeros((N + 2, N + 2), dtype=np.int64) -for i, a in enumerate(A[1:], 1): -    if a >= 0: -        graph[start, i] = a -    else: -        graph[i, goal] = -a -for i in range(1, N + 1): -    for j in range(2 * i, N + 1, i): -        if A[i] < 0 and A[j] > 0: -            graph[j][i] = INF +N, *A = list(map(int, read().split())) -def max_flow(graph): -    flow = 0 -    while True: -        dist, pred = dijkstra( -            graph, indices=start, return_predecessors=True, unweighted=True -        ) -        if dist[goal] == np.inf: -            return flow -        path = [] -        v = goal +class Dinic: +    def __init__(self, N, source, sink): +        self.N = N +        self.G = [[] for _ in range(N)] +        self.source = source +        self.sink = sink + +    def add_edge(self, fr, to, cap): +        n1 = len(self.G[fr]) +        n2 = len(self.G[to]) +        self.G[fr].append([to, cap, n2]) +        self.G[to].append([fr, 0, n1])  # 逆辺を cap 0 で追加 + +    def add_edge_undirected(self, fr, to, cap): +        n1 = len(self.G[fr]) +        n2 = len(self.G[to]) +        self.G[fr].append([to, cap, n2]) +        self.G[to].append([fr, cap, n1]) + +    def bfs(self): +        level = [0] * self.N +        G = self.G +        source = self.source +        sink = self.sink +        q = deque([source]) +        level[source] = 1 +        pop = q.popleft +        append = q.append +        while q: +            v = pop() +            lv = level[v] + 1 +            for to, cap, rev in G[v]: +                if not cap: +                    continue +                if level[to]: +                    continue +                level[to] = lv +                if to == sink: +                    self.level = level +                    return +                append(to) +        self.level = level + +    def dfs(self, v, f): +        if v == self.sink: +            return f +        G = self.G +        prog = self.progress +        level = self.level +        lv = level[v] +        E = G[v] +        for i in range(prog[v], len(E)): +            to, cap, rev = E[i] +            prog[v] = i +            if not cap: +                continue +            if level[to] <= lv: +                continue +            x = f if f < cap else cap +            ff = self.dfs(to, x) +            if ff: +                E[i][1] -= ff +                G[to][rev][1] += ff +                return ff +        return 0 + +    def max_flow(self): +        INF = 10**18 +        flow = 0 -            path.append((pred[v], v)) -            v = pred[v] -            if v == start: -                break -        add_flow = min(graph[x][y] for x, y in path) -        for x, y in path: -            graph[x][y] -= add_flow -            graph[y][x] += add_flow -        flow += add_flow +            self.bfs() +            if not self.level[self.sink]: +                return flow +            self.progress = [0] * self.N +            while True: +                f = self.dfs(self.source, INF) +                if not f: +                    break +                flow += f +        return flow -answer = sum(x for x in A if x > 0) - max_flow(graph) +source = 0 +sink = N + 1 +INF = 10**18 +dinic = Dinic(N + 2, source, sink) +add = dinic.add_edge +for i, x in enumerate(A, 1): +    if x < 0: +        # source側：割るものを表現。sink側にうつすときにカット-xが必要。 +        add(source, i, -x) +    else: +        # sink側：割らないものを表現。source側にうつすときにカットxが必要。 +        add(i, sink, x) +for i in range(1, N + 1): +    for j in range(i + i, N + 1, i): +        # iを割るならjも割る。iを割ってjを割らないのは禁止 +        # iがsourceでjがsinkなのは禁止 +        add(i, j, INF) +f = dinic.max_flow() +x = sum(x for x in A if x >= 0) +answer = x - f