编写一个 Python 函数，接受两个整数作为参数并返回它们的最小公倍数。
def lcm(a, b):
  if a > b:
    greater = a
  else:
    greater = b
  while(True):
    if((greater % a == 0) and (greater % b == 0)):
      lcm = greater
      break
    greater += 1
  return lcm

print(lcm(15, 18))
# 输出: 90