Time Limit: 6000 ms
Memory Limit: 65535 ms
As the chairman of Technology Association, Xiaoyoulei has Obtained great achievements on the ability of “Huyou”and ,done great contributions on the construction of our school.
Our school is so big that every small costs turns to be huge after being multiplied by the number of people living here and the area of school. As the inflation nowadays, it becomes more and more important to decline the costs.
To reduce the Electric costs of NJUST, Xiaoyouleihas decided to optimize the road lighting. Till now every road was illuminated all night long, which costs 1 yuan per meter and day. To save money, he decided to no longer illuminate every road, but to switch off the road lighting of some streets. To make sure that the inhabitants of NJUST still feel safe, he want to optimize the lighting in such a way, that after darkening some streets at night, there will still be at least one illuminated path from every crossing in NJUST to every other crossing.
What is the maximum daily amount of money Xiaoyoulei can save, without making their inhabitants feel unsafe?