import heapq

INF = 1 << 60

n, m, p = map(int, input().split())
a = list(map(int, input().split()))

if any([x > m for x in a]):
  print("1")
  exit()

idx = {}
q = []
for i in range(n):
  cur = a[i]
  cnt = 1
  while cur % p == 0:
    cnt += 1
    cur //= p

  q.append((a[i], cur))

  if idx.get(cnt, None) is None or a[idx[cnt]] < a[i]:
    idx[cnt] = i

dist = {}
dist[1] = 0
hp = [(0, 1)]
ans = INF
while len(hp) > 0:
  cd, cur = heapq.heappop(hp)
  if cd > dist[cur]:
    continue

  for cost, i in idx.items():
    ai, d = q[i]
    nxt = cur * ai
    if dist.get(nxt, INF) > dist[cur] + 1:
      if nxt > m:
        ans = min(ans, dist[cur] + 1)
    nxt = cur * d
    if dist.get(nxt, INF) > dist[cur] + cost:
      if nxt > m:
        ans = min(ans, dist[cur] + cost)
      else:
        dist[nxt] = dist[cur] + cost
        heapq.heappush(hp, (dist[nxt], nxt))

if ans < INF:
  print(ans)
else:
  print("-1")