Background

Description

Format

Input

Output

Sample 1

Input

4
1 2 1
1 4 2
1 3 2
2 4 1

Output

2.0

Sample 2

Input

5
1 5 100
2 1 77
3 2 80
4 1 64
5 3 41

Output

109.0

Limitation

Hint

Source

CDQZ TEST