mod = 1000000007
eps = 10**-9
inf = 10**17


def main():
    import sys
    input = sys.stdin.readline

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

    if max(A) > M:
        print(1)
        exit()

    B = [1] * 40
    for a in A:
        cnt = 0
        aa = a
        while aa % P == 0:
            cnt += 1
            aa //= P
        B[cnt] = max(B[cnt], aa)

    dp = [[-inf] * 40 for _ in range(40)]
    dp[0][0] = 1
    ans = inf
    ma = max(A)
    for i in range(40):
        for j in range(40):
            if i != 0:
                dp[i][j] = dp[i-1][j]
            if j - i - 1 >= 0:
                dp[i][j] = max(dp[i][j], dp[i][j-i-1] * B[i])
            if dp[i][j] * ma > M:
                ans = min(ans, j+1)
    if ans != inf:
        print(ans)
    else:
        print(-1)


if __name__ == '__main__':
    main()