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输入样例1

3 3 
1 2 1 3 
2 3 2 2 
3 1 3 1

输出样例1

5.830952

输入样例2

6 9 
1 2 4 -1 
2 3 4 1 
3 4 -1 -5 
1 5 -4 0 
4 6 1 -6 
2 6 -6 0 
5 6 -7 5 
2 4 7 1 
1 4 -9 -5

输出样例

27.459060