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: print(input()[0] + input([1]) + input()[2])
  
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"}]