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单点时限: 2.0 sec
内存限制: 256 MB
At the foot of Mt.Byte there is an entrance to a cave. The cave consists of a complex system of chambers connected with tunnels. The cave entrance leads straight to a chamber called the front chamber. The tunnels do not intersect (they meet only in chambers). Two chambers can either be connected with a single tunnel, or not be connected at all (it may, however, be possible to reach one chamber from the other via remaining chambers). A tunnel always connects two distinct chambers.
It has been decided that ‘King’s of Byteotia Cup’ competition is to be organized. The goal of each competitor is to traverse a freely chosen route in the cave and get out as quickly as possible. The route has to lead through at least one other chamber than the front one. Only two rules are in force: during the travel through the cave each chamber (with the exception of the front chamber) can be visited once at the most, similarly each corridor cannot be crossed more than once.
A fameous cave explorer Byteala is preparing himslef for the competition. Byteala has been training in the cave for a long time and he has acquired a detailed knowledge of the corridor system. For each corridor he has calculated the amount of time needed to cross it in each direction. The time necessary to move within the chambers can be neglected. Now Byteala would like to calculate a route satisfying requirements of the competition, which can be traversed in the least time possible (the time necessary to traverse a route is the sum of the times needed to cross corridors which it consists of).
Task
Help Byteala! Write a programme which:
reads from the standard input a description of the cave and times necessary to cross each corridor,
calculates a route consistent with the requirements, for which the sum of times needed to cross the corridors it comprises is minimal,
writes to the standard output the time required to traverse the calculated route.
In the first line of the input there are two integers n and m (3 <= n <= 5000, 3 <= m <= 10000) separated by a single space denoting the number of chambers in the cave and the number of interlinking corridors, respectively. The chambers are numbered from 1 to n. The front chamber is denoted by 1. The following m lines contain a description of the corridors. In each of these lines there are four integers separated by single spaces. A 4-tuple a,b,c,d means that chambers a and b are connected with a corridor, the crossing time from a to b is c and from b to a is d, 1 <= a,b <= n, a <> b, 1 <= c,d <= 10000. You can assume that a route satisfying requirements of the competition always exists.
Your programme should write in the first (and only) line of the output one integer - the minimal time required to traverse a route satisfying conditions of the competition.
3 3 1 2 4 3 2 3 4 2 1 3 1 1
6
0 人解决，0 人已尝试。
0 份提交通过，共有 0 份提交。
9.9 EMB 奖励。