require 'prime'
n=gets.to_i
dp=[0]*(n+2)
x=Prime.each(n).to_a
t=n/2+2
sum=0
while (x.empty? == false) && (x[0]*2<=n)
	e=x.shift
	sum+=e
	sum=[n,sum].min
	(sum-e+1).times{|i|
		p2=(sum-e+1)-i
		p3=e+p2
		next if p3>n
		if dp[p2]>0 && dp[p3]<dp[p2]+1
			dp[p3]=dp[p2]+1
		end
	}
	dp[e]=[dp[e],1].max
end
ans=dp[n]
x.each{|e|
	p1=n-e
	break if p1<0
	if ans<dp[p1]+1
		ans=dp[p1]+1
	end
	
}
if ans<1
	puts -1
else
	puts ans
end