input: Write a function to search for a given word in a large document and return the line number where the word is found. The function should return the line number as an integer. If the word is not found in the document, the function should return -1.
  assert findWord('This is the first line of the document.\nThis is the second line of the document.\nThis is the third line of the document.', 'second')==2
  assert findWord('This is the first line of the document.\nThis is the second line of the document.\nThis is the third line of the document.', 'fourth')==-1
  assert findWord('This is the first line of the document.\nThis is the second line of the document.\nThis is the third line of the document.', 'first')==1
  assert findWord('', 'any')==-1
  assert findWord('Single line document', 'document')==1
output: def findWord(document, word):
      lines = document.split('\n')
      for i, line in enumerate(lines):
          if word in line:
              return i + 1
      return -1