require 'Prime'

n = gets.to_i

def func(n)
	arr = [-1,-1,-1,-1,3,0,5,0,7,7,7,0,11,0,13,7,7,0,8,0,19,19,7,0,23,23,8,8,8,0,8,0,8,8,8,8,8,0,8,8,8,0,8,0,8,8,8,0,-1]

	if(n<48) then
		return arr[n]
	end
	if n%8==1 && Prime.prime?(n-8) then 
		return 14
	else
		return 8
	end
end


puts func(n)