n,m,p = gets.to_s.split.map{ |v| v.to_i }
a = gets.to_s.split.map{ |v| v.to_i }
b = a.map do |v|
  x = v
  while x >= p && x % p == 0
    x /= p
  end
  x
end

am = a.max
bm = b.max

if am < m && bm == 1
  puts -1
  exit
end

ans = 0
x = 1
while x <= m
  ans += 1
  if x * am <= m
    x *= bm
  else
    x *= am
  end
end
puts ans