N, M, P = gets.split.map(&:to_i)
A = gets.split.map(&:to_i)

ans = Float::INFINITY
max_e = 1

A.each do |a|
  div_cnt = 0
  e = a

  while e % P == 0
    e /= P
    div_cnt += 1
  end

  next if e == 1

  cnt = 0
  x = 1
  while x * a <= M
    x *= e
    cnt += (1 + div_cnt)
  end

  if ans > cnt + 1
    ans = cnt + 1
  end
end

if ans == Float::INFINITY
  puts -1
else
  puts ans
end