N = gets.to_i

base = []
1.upto(9) do |a|
  (a + 1).upto(9) do |b|
    base << 10 * a + b
  end
end

len = base.size
idx = (N - 1) % len
row = (N - 1) / len

x = base[idx].to_s
row.times do
  x << x[-1]
end

puts x