思路：先儘可能多地使用大的，再使用小的
1）用了多少塊大的：min(big, goal / 5)
2）還需要多少塊小的：goal - 5 * min(big, goal / 5)
def make_bricks(small, big, goal):
if goal / 5 <= big:
return goal % 5 <= small
else:
return goal - big * 5 <= small
更簡潔的寫法：
def make_bricks(small, big, goal):
return goal - 5 * min(big, goal/5) <= small
