def fun142(start, stop):
sta = start.split(':')
A = int(sta) * 3600 + int(sta) * 60 + int(sta)
end = stop.split(':')
B = int(end) * 3600 + int(end) * 60 + int(end)
return '时间差为：' + str(B - A if B > A else 86400 + B - A) + 's'
start = '17:55:31'
stop = '24:21:57'
print(fun142(start, stop))