lib C
  fun strtoll(s : UInt8*, p : UInt8**, b : Int32) : Int64
end

class String
  def to_i64
    C.strtoll(self, nil, 10)
  end
end

n, m, k = read_line.split.map(&.to_i64)
a = read_line.split.map(&.to_i64)
b, cnt = a.map { |i|
  c = 1
  while i % k == 0
    i //= k
    c += 1
  end
  [i, c]
}.transpose

if b.max == 1
  puts -1
  exit
end

goal = m // a.max + 1
dp = [0] * 64
dp[0] = 1
(0...64).each do |x|
  (0...n).each do |i|
    if dp[x] < goal && x + cnt[i] < 64
      dp[x + cnt[i]] = {dp[x + cnt[i]], dp[x] * b[i]}.max
    end
  end
end
puts dp.index { |i| i >= goal }.not_nil! + 1