input: Write a python function to determine the highest factor of a given number n, which is less than n and divides n without remainder.
  assert largest_divisor(3) == 1
  assert largest_divisor(7) == 1
  assert largest_divisor(10) == 5
  assert largest_divisor(100) == 50
  assert largest_divisor(49) == 7
output: def largest_divisor(n):
      for i in range(n // 2, 0, -1):
          if n % i == 0:
              return i