input: Write a python function that, given a number n, determines the greatest number less than n that divides n without a 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