output_description: Print the desired string in one line.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S
      w
attempt: import sys
  
  stdin = sys.stdin
  inf = 1 << 60
  mod = 1000000007
  
  ni = lambda: int(ns())
  nin = lambda y: [ni() for _ in range(y)]
  na = lambda: list(map(int, stdin.readline().split()))
  nan = lambda y: [na() for _ in range(y)]
  nf = lambda: float(ns())
  nfn = lambda y: [nf() for _ in range(y)]
  nfa = lambda: list(map(float, stdin.readline().split()))
  nfan = lambda y: [nfa() for _ in range(y)]
  ns = lambda: stdin.readline().rstrip()
  nsn = lambda y: [ns() for _ in range(y)]
  ncl = lambda y: [list(ns()) for _ in range(y)]
  nas = lambda: stdin.readline().split()
  
  s = ns()
  w = ni()
  
  i = 0
  while i < len(s):
      print(s[i], end="")
      i += w
  
  print()
  
problem_description: Statement
  
  You are given a string S consisting of lowercase English letters. We will
  write down this string, starting a new line after every w letters. Print the
  string obtained by concatenating the letters at the beginnings of these lines
  from top to bottom.
samples: [{"input": "abcdefgh\n    3", "output": "adg\n    \n\nWhen we write down `abcdefgh`, starting a new line after every three letters,\nwe get the following:\n\nabc  \ndef  \ngh\n\nConcatenating the letters at the beginnings of these lines, we obtain `adg`.\n\n* * *"}, {"input": "lllll\n    1", "output": "lllll\n    \n\n* * *"}, {"input": "souuundhound\n    2", "output": "suudon"}]