15 prom

# (x in A + x in P) + (x in Q <= x in R)
def xin(x, a):
    return a[0] <= x <= a[1]

def f(x, a):
    p = (10, 40)
    q = (5, 15)
    r = (35, 50)
    return (xin(x, a) or xin(x, p)) or (xin(x, q) <= xin(x, r))

nums = [5, 10, 15, 35, 40, 50]
nums.sort()
min_l = 10000
for i in range(len(nums)):
    for j in range(i+1, len(nums)):
        for x in range(1, 10000):
             a = (nums[i], nums[j])
             if not f(x, a):
                 break
        else:
            print(nums[i], nums[j])
            min_l = min(min_l, nums[j] - nums[i])
print(min_l)

# nums = [5, 10, 15, 35, 40, 50]
# nums.sort()
# min_l = 10000
# for a1 in range(5, 50+1):
#     for a2 in range(a1+1, 50+1):
#         for x in range(1, 10000):
#             a = (a1, a2)
#             if not f(x, a):
#                 break
#         else:
#             print(a1, a2)
#             if a1 in nums and a2 in nums:
#                 min_l = min(min_l, a2 - a1)
# print(min_l)