require "prime"

def h(n)
  # while n > 10
  #   n = n.to_s.chars.map(&:to_i).inject(0,:+)
  # end
  # n
  while n > 10
    r = 0
    while n > 0
      n, m = n.divmod(10)
      r += m
    end
    n = r
  end
  n
end

def f(k, n)
  primes = Prime.each(n).drop_while{|n| n < k}

  last = -1
  max = 0
  r = []
  primes.each_with_index{|_v,i|
    # break if i + max > primes.size

    v = h(_v)
    idx = r.index(v)
    r.shift(idx+1) if idx
    r << v
    max = [max, r.size].max
    last = i if r.size >= max
  }
  primes[last-max+1]
end


K = gets.to_i
N = gets.to_i
p f(K, N)