require 'prime'
p Enumerator.new{|y|
	(2..1/0.0).each{|i|
		a=i.prime_division
		y<<i if (a.size==2&&a.all?{|e|e[1]==1}) || (a.size==1&&a[0][1]==3)
	}
}.take(gets.to_i).last