OJ Board

Can anyone tell me how to solve this problem efficiently?

Well , I know what you mean now .
Thank you very much

what is the meaning of maximum safe travel distance?
if the distance from origin to right tangent is smaller than the distance
from origin to left,which should I output?

Can anyone tell me why the sample output should be 2.400
with input 5 5 1 12 12

I don't know why,and now the submit-0-matic seems not work.

my output code:
[cpp] printf("%5d -> %d\n",n,sum);


I got pe and can't understand why. [/cpp][/code]

Then I really can't understand why I get WA.Is there anything tricky in this problem?

Can anyone tell me what does "Lexicographically" mean?
Is sequence "1 2 3 4" less than "4 3 2 1"?

I can't understand the problem.Can anyone tell me?