
# 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:

n = int(eval(input()))

ans = 0

SQRT = int(n ** 0.5)

for m in range(1,SQRT + 1):

    b = int(n/m)

    ans += m * (m + b) * (b + 1 - m)

ans -= SQRT * (SQRT+1) * (2*SQRT+1) // 6

print(ans)

# optimized version of the same code:

def main():

  n = int(eval(input()))

  ans = 0

  SQRT = int(n ** 0.5)

  for m in range(1,SQRT + 1):

    b = int(n/m)

    ans += m * (m + b) * (b + 1 - m)

  ans -= SQRT * (SQRT+1) * (2*SQRT+1) // 6

  print(ans)

main()

n = int(eval(input()))
ans = 0
SQRT = int(n**0.5)
for m in range(1, SQRT + 1):
    b = int(n / m)
    ans += m * (m + b) * (b + 1 - m)
ans -= SQRT * (SQRT + 1) * (2 * SQRT + 1) // 6
print(ans)

def main():
    n = int(eval(input()))
    ans = 0
    SQRT = int(n**0.5)
    for m in range(1, SQRT + 1):
        b = int(n / m)
        ans += m * (m + b) * (b + 1 - m)
    ans -= SQRT * (SQRT + 1) * (2 * SQRT + 1) // 6
    print(ans)


main()

-n = int(eval(input())) -ans = 0 -SQRT = int(n**0.5) -for m in range(1, SQRT + 1): -    b = int(n / m) -    ans += m * (m + b) * (b + 1 - m) -ans -= SQRT * (SQRT + 1) * (2 * SQRT + 1) // 6 -print(ans) +def main(): +    n = int(eval(input())) +    ans = 0 +    SQRT = int(n**0.5) +    for m in range(1, SQRT + 1): +        b = int(n / m) +        ans += m * (m + b) * (b + 1 - m) +    ans -= SQRT * (SQRT + 1) * (2 * SQRT + 1) // 6 +    print(ans) + + +main()