13. 解决方案：While 循环
练习解决方案：最接近的平方数
limit = 40
num = 0
while (num+1)**2 < limit:
num += 1
nearest_square = num**2
print(nearest_square)输出：
36limit = 40
num = 0
while (num+1)**2 < limit:
num += 1
nearest_square = num**2
print(nearest_square)36