func main()
	var n: int :: cui@inputInt()
	var ans: int :: 0
	if(n >= 2)
		for r(3, n, 2)
			if(!math@prime(r))
				skip r
			end if
			if(r * r > 2 * n)
				break r
			end if
			var p: int :: 2
			var q: int :: r * r - 2
			if(0 < q & q <= n & math@prime(q))
				do ans :+ 1
			end if
		end for
		do ans :* 2
		do ans :+ 1
	end if
	
	do cui@print("\{ans}\n")
end func