import sys

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

def main(N, M, p, A):
    # A = B * P^K
    B = [0] * N
    K = [0] * N
    for i, x in enumerate(A):
        e = 0
        while x % p == 0:
            e += 1
            x //= p
        B[i], K[i] = x, e
    # というか、K ごとの max_A
    AA = [0] * 30
    BB = [0] * 30
    for a, b, k in zip(A, B, K):
        if AA[k] < a:
            AA[k] = a
            BB[k] = b
    A, B = AA, BB
    # 総コストごとに、ベストな x
    MAX = 500
    D = [1] * (MAX * 2)
    for i in range(MAX):
        x = D[i]
        for k in range(30):
            a, b = A[k], B[k]
            if a == 0:
                continue
            if x * a > M:
                return i + 1
            to = x * b
            D[i + k + 1] = max(D[i + k + 1], to)
    return -1

N, M, P = map(int, readline().split())
A = list(map(int, readline().split()))

print(main(N, M, P, A))