N,M,P = map(int,input().split())
A = list(map(int,input().split()))
INF = 10 ** 9
ans = INF
for i in range(N):
    a = A[i]
    while a % P == 0:
        a //= P
    if a > 1:
        cnt = 0
        now = 1
        while M >= now:
            now *= a
            cnt += 1
        ans = min(ans,cnt)
if ans == INF:
    print(-1)
else:
    print(ans)