input: Write a function to determine if a number provided by the user is prime or not. The function should return True if the number is prime and False otherwise. If the input number is less than 2, the function should return False.
  
  assert is_prime(17)==True
  assert is_prime(15)==False
  assert is_prime(2)==True
  assert is_prime(1)==False
  assert is_prime(-1)==False
output: def is_prime(n):
      if n < 2:
          return False
      for i in range(2, int(n**0.5) + 1):
          if n % i == 0:
              return False
      return True