text: str = input("Input sentence: ")
  ans=''
  t = int(input("Input row: "))
  arr = [['0']*100 for i in range(t)]
  status = True
  r = -1
  c = 0
  for i in str:
      if status :
          r+=1
          arr[r][c] = i
      else :
          r-=1
          c+=1
          arr[r][c] = i
      if (r == t-1)  or  ( (r == 0) and (c != 0) ) :
          status = not status
  for i in range(len(arr)):
      for j in range(len(arr[0])):
          if arr[i][j] != '0':
              ans = ans + arr[i][j]
  print(ans)