r = STDIN.gets.to_f
#
# r = 34.1201
#
#
#
 puts "#{ sprintf("%.6f",r*r*Math::PI) } #{sprintf("%.6f", r*2*Math::PI )}"
#





# r = 2
# res = r*r*Math::PI
#
# def s(v)
#   sprintf("%.6f", v)
# end
#
# p s(res)

