N, M, P = map(int, input().split())
A = list(map(int, input().split()))
maxa = max(A)
from collections import defaultdict
dp = defaultdict(lambda: 0)
cnts = [1]*30
for i in range(N):
  cnt = 0
  while A[i]%P==0:
    cnt += 1
    A[i] //= P
  cnts[cnt] = max(cnts[cnt], A[i])
dp[0] = 1
if max(A)==1 and maxa<=M:
  print(-1)
  exit()
ans = 0
p = 1
while p*maxa <= M:
  for i in range(30):
    dp[ans+i+1] = max(dp[ans+i+1], p*cnts[i])
  ans += 1
  p = dp[ans]
if p>M:
  print(ans)
else:
  print(ans+1)