B. Pen spinning accident
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

See PDF statement in attachment.

Examples
Input
1 0 0
0 0 1
1 0 0

0 1 0
0 1 0
0 0 1
Output
0.785398163397
Input
1 0 0
0 0 1
1 0 0

0 1 0
0 1 0
0 0 -1
Output
never
Input
0 0 0
1 0 0
0 1 0

0 0 1
0 1 0
-1 0 0
Output
never
Input
1 0 0
-1 0 -1
-1 0 1

0 1 0
0 1 0
0 0 1
Output
0.392699081699
Input
0 0 1
0 -1 1
0 1 1

-1 0 -1
-1 0 0
0 -1 0
Output
0.511669644114
Input
0 -1 0
-1 0 0
0 0 -1

1 0 0
0 0 -1
0 1 0
Output
0.785398163397