import heapq
import bisect
from collections import defaultdict
inf = 10 ** 18


N, M, P = map(int, input().split())
A = list(map(int, input().split()))
last = max(A)

if last > M:
    print(1)
    exit()

dist = defaultdict(lambda: inf)
edge = defaultdict(lambda: inf)
found = False
for a in A:
    cnt = 1
    while a % P == 0:
        a //= P
        cnt += 1
    if a == 1:
        continue
    edge[a] = min(edge[a], cnt)
    found = True

if not found:
    print(-1)
    exit()

que = [(0, 1)]
dist[1] = 0
while que:
    ds, s = heapq.heappop(que)
    if dist[s] < ds:
        continue
    if s * last > M:
        print(ds + 1)
        break
    for t, dt in edge.items():
        next = s * t
        if dist[next] > ds + dt:
            dist[next] = ds + dt
            heapq.heappush(que, (ds + dt, next))