Some tests were added. The checker precision was decreased. Look the statement for some changes in "Output" paragraph.

The problem has been rejudged. Some authors lost AC, and some get.

Many thanks to Fyodor Menshikov for new tests and help during the investigation.

Edited by author 19.01.2007 17:43

After changes especially after diminishing of precision
problem became absolutely simple and solvable numerically
by strict search on sequence of grids in double type
Last variant was very interesting due 1.e-8