M = 5_000_000

n = gets.to_s.to_i
a = gets.to_s.split.map(&.to_i)
b = Array.new(10, false)
a.each { |x| b[x] = true }

is_prime = Array.new(M + 1, true)
primes = [] of Int32

(2..M).each do |i|
  next unless is_prime[i]
  primes << i
  j = 2 * i
  while j <= M
    is_prime[j] = false
    j += i
  end
end

primes << M + 1

solve = ->(p : Int32) do
  res = Array.new(10, false)
  num = p
  while num > 0
    res[num % 10] = true
    num //= 10
  end
  res
end

now = Array.new(10, false)
ans = -1
last = 0

(0...primes.size - 1).each do |i|
  c = solve.call(primes[i])
  flag = false

  (0..9).each do |j|
    if c[j] && !b[j]
      flag = true
      break
    end
  end

  if flag
    (0..9).each { |j| now[j] = false }
    last = primes[i]
    next
  end

  (0..9).each { |j| now[j] = true if c[j] }

  if b == now
    candidate = primes[i + 1] - last - 2
    ans = candidate if candidate > ans
  end
end

puts ans