>

In your solution I'm sure there is "result=2*pi*r" and then you add
distances between centers of the circles, don't you? And so the parts
of circles where rope touches is exactly P or C (2*pi*r).

i try to read ur msg for many times .But i don't understand what u want
to tell (sorry my english was very bad)
but anyway i prove it(after i've got AC)
i see that a radius is perpendicular with a line that touch circle
and then a total of angle in each circle is 360
:-) hope u can understand it
> In your solution I'm sure there is "result=2*pi*r" and then you add
> distances between centers of the circles, don't you? And so the parts
> of circles where rope touches is exactly P or C (2*pi*r).