N, M, P = map(int, input().split())
A = list(map(int, input().split()))
if M == 1:
    print(0)
    exit()

last = max(A)   # これ、最後に必ずかける
target = (M + last - 1) // last

if target == 1:
    print(1)
    exit()

ans = 10 ** 18
for a in A:
    cnt = 1
    x = a
    while x % P == 0:
        cnt += 1
        x //= P
    if x == 1:
        continue

    tmp = cnt * ((target + x - 1) // x) + 1
    ans = min(ans, tmp)

if ans >= 10 ** 18:
    ans = -1
print(ans)