input: Write a python function to find the LCM (Least Common Multiple) of two numbers using the provided gcd function.
  assert lcm(12, 15) == 60
  assert lcm(7, 5) == 35
  assert lcm(21, 6) == 42
output: def lcm(a, b):
      def gcd(x, y):
          while y:
              x, y = y, x % y
          return x
  
      return abs(a * b) // gcd(a, b)