Goat in the garden

Someone has let a goat in a square kitchen-garden and had bound it to a stake. The stake is driven into the ground in the very midst of the square. The goat is hungry as a hunter and very voracious, and eats everything that can be reached without leaving the square and tearing off the rope. What area of the kitchen-garden will be ate round?

Input

Contains lengths of the garden sides a and a cord length r in meters (positive integers not exceeding 100).

Output

Print the area of the kitchen-garden (in square meters to within 6 symbols after a decimal point), ate round by the goat.

Examples