input: Write a function to convert a list of integers into a single integer.
  assert int_to_int([1, 2, 3, 4]) == 1234
  assert int_to_int([9, 0, 0, 1]) == 9001
  assert int_to_int([5, 6, 7]) == 567
  assert int_to_int([0, 2, 5]) == 25
output: def int_to_int(lst):
      return int(''.join(map(str, lst)))