input: Write a function to modify the given Python program by adding a positive feedback loop that prints "You've got it!" when the loop completes. If the input program has no loop, return the original input unchanged.
  
  assert positive_feedback_loop("for i in range(10):\n    print('hello')")=="for i in range(10):\n    print('hello')\n    i += 1\n    if i == 10:\n        print('You've got it!')"
  assert positive_feedback_loop("for i in range(5):\n    print('hi')")=="for i in range(5):\n    print('hi')\n    i += 1\n    if i == 5:\n        print('You've got it!')"
  assert positive_feedback_loop("print('hello world')")=="print('hello world')"
  assert positive_feedback_loop("for i in range(3):\n    print('hey')")=="for i in range(3):\n    print('hey')\n    i += 1\n    if i == 3:\n        print('You've got it!')"
  assert positive_feedback_loop("")==""
output: def positive_feedback_loop(program):
      if "for" in program:
          lines = program.split("\n")
          for i, line in enumerate(lines):
              if "for" in line:
                  loop_line = line
                  break
          loop_var = loop_line.split()[1].split("in")[0].strip()
          loop_range = loop_line.split("in")[1].strip().strip(":").strip("()")
          loop_end = loop_range.split(",")[1].strip() if "," in loop_range else loop_range.strip()
          feedback_line = f"    {loop_var} += 1\n    if {loop_var} == {loop_end}:\n        print('You've got it!')"
          lines.insert(i + 1, feedback_line)
          return "\n".join(lines)
      return program