output_description: Print the string of length 3 that can be obtained by concatenating the letters
  on the diagonal connecting the top-left and bottom-right corner of the grid,
  from the top-left to bottom-right.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      c_{11}c_{12}c_{13}
      c_{21}c_{22}c_{23}
      c_{31}c_{32}c_{33}
attempt: import sys
  
  sys.setrecursionlimit(1 << 25)
  read = sys.stdin.readline
  ra = range
  enu = enumerate
  
  
  def read_ints():
      return list(map(int, read().split()))
  
  
  def read_a_int():
      return int(read())
  
  
  def read_tuple(H):
      """
      H is number of rows
      """
      ret = []
      for _ in range(H):
          ret.append(tuple(map(int, read().split())))
      return ret
  
  
  def read_col(H):
      """
      H is number of rows
      A列、B列が与えられるようなとき
      ex1)A,B=read_col(H)    ex2) A,=read_col(H) #一列の場合
      """
      ret = []
      for _ in range(H):
          ret.append(list(map(int, read().split())))
      return tuple(map(list, zip(*ret)))
  
  
  def read_matrix(H):
      """
      H is number of rows
      """
      ret = []
      for _ in range(H):
          ret.append(list(map(int, read().split())))
      return ret
      # return [list(map(int, read().split())) for _ in range(H)] # 内包表記はpypyでは遅いため
  
  
  MOD = 10**9 + 7
  INF = 2**31  # 2147483648 > 10**9
  # default import
  from collections import defaultdict, Counter, deque
  from operator import itemgetter
  from itertools import product, permutations, combinations
  from bisect import bisect_left, bisect_right  # , insort_left, insort_right
  
  # https://atcoder.jp/contests/abc090/tasks/abc090_a
  
  C = []
  for i in ra(3):
      print(input()[i], end="")
  
problem_description: Statement
  
  We have a 3×3 square grid, where each square contains a lowercase English
  letters. The letter in the square at the i-th row from the top and j-th column
  from the left is c_{ij}.
  
  Print the string of length 3 that can be obtained by concatenating the letters
  in the squares on the diagonal connecting the top-left and bottom-right corner
  of the grid, from the top-left to bottom-right.
samples: [{"input": "ant\n    obe\n    rec", "output": "abc\n    \n\nThe letters in the squares on the diagonal connecting the top-left and bottom-\nright corner of the grid are `a`, `b` and `c` from top-right to bottom-left.\nConcatenate these letters and print `abc`.\n\n* * *"}, {"input": "edu\n    cat\n    ion", "output": "ean"}]