#!/usr/bin/ruby
B=10
q=gets.to_i/(10**9+1)
p Enumerator.new{|y|
	1.step(B-1){|e|y<<e}
	s=1
	loop{
		s.step(s*B-1){|i|
			x=i.to_s
			y<<(x+x.reverse).to_i
		}
		s.step(s*B-1){|i|
			x=i.to_s
			0.step(B-1){|mid|
				y<<(x+mid.to_s+x.reverse).to_i
			}
		}
		s*=10
	}
}.take_while{|e|e<=q}.size