def processing diff_arr
  indexes = _indexes_of_changed_lines diff_arr
  indexes.each do |index|
    first_line = diff_arr[index+1]
    second_line = diff_arr[index+2]
    max_length = [first_line.size, second_line.size].max
    first_the_same_symbols = 0
    (0..max_length + 1).each do |i|
      first_the_same_symbols = i - 1
      if first_line[i] != second_line[i] && i > 0
        break
      end
    end
    first_token = first_line[0..first_the_same_symbols][1..-1]
    diff_arr[index+1].sub!(first_token, first_token + START)
    diff_arr[index+2].sub!(first_token, first_token + START)
    last_the_same_symbols = 0
    (1..max_length + 1).each do |i|
      last_the_same_symbols = -i
      shortest_line = second_line.size > first_line.size ? first_line : second_line
      if ( first_line[-i] != second_line[-i] ) || "#{first_token}#{START}".size == shortest_line[1..-i].size
        break
      end
    end
    last_the_same_symbols += 1
    last_token = first_line[last_the_same_symbols..-1]
    diff_arr[index+1].sub!(%r#{Regexp.escape(last_token)}$/, FINISH + last_token)
    diff_arr[index+2].sub!(%r#{Regexp.escape(last_token)}$/, FINISH + last_token)
  end
  diff_arr
end