Codeforces Round #250 (Div. 1) A. The Child and Toy

本文介绍了一个有趣的算法问题:如何以最小的能量消耗拆解一个由多个部分组成的玩具。问题设定为儿童节礼物,通过一系列数学规则定义了玩具各部分间的连接方式及移除所需的能量值。文章提供了样例输入输出,并解释了最优解策略。

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A. The Child and Toy
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

On Children's Day, the child got a toy from Delayyy as a present. However, the child is so naughty that he can't wait to destroy the toy.

The toy consists of n parts and m ropes. Each rope links two parts, but every pair of parts is linked by at most one rope. To split the toy, the child must remove all its parts. The child can remove a single part at a time, and each remove consume an energy. Let's define an energy value of part i as vi. The child spend vf1 + vf2 + ... + vfk energy for removing part i where f1, f2, ..., fk are the parts that are directly connected to the i-th and haven't been removed.

Help the child to find out, what is the minimum total energy he should spend to remove all n parts.

Input

The first line contains two integers n and m (1 ≤ n ≤ 10000 ≤ m ≤ 2000). The second line contains n integers: v1, v2, ..., vn (0 ≤ vi ≤ 105). Then followed m lines, each line contains two integers xi and yi, representing a rope from part xi to part yi (1 ≤ xi, yi ≤ nxi ≠ yi).

Consider all the parts are numbered from 1 to n.

Output

Output the minimum total energy the child should spend to remove all n parts of the toy.

Sample test(s)
input
4 3
10 20 30 40
1 4
1 2
2 3
output
40
input
4 4
100 100 100 100
1 2
2 3
2 4
3 4
output
400
input
7 10
40 10 20 10 20 80 40
1 5
4 7
4 5
5 2
5 7
6 4
1 6
1 3
4 3
1 4
output
160
Note

One of the optimal sequence of actions in the first sample is:

  • First, remove part 3, cost of the action is 20.
  • Then, remove part 2, cost of the action is 10.
  • Next, remove part 4, cost of the action is 10.
  • At last, remove part 1, cost of the action is 0.

So the total energy the child paid is 20 + 10 + 10 + 0 = 40, which is the minimum.

In the second sample, the child will spend 400 no matter in what order he will remove the parts.


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