import bisect
import heapq
inf = 2 * 10 ** 18


def gen_div(N):
    yield 1
    for i in range(2, N+1):
        if i * i > N:
            break
        if N % i == 0:
            yield i
            if i * i != N:
                yield N // i
    yield N


N, M, A, B = map(int, input().split())
C = sorted(map(int, input().split()))

ans = inf
divisors_of_N = sorted(gen_div(N))
K = len(divisors_of_N)
dtoi = {d: i for i, d in enumerate(divisors_of_N)}


dp = [[inf] * K for _ in range(K)]
dp[0][0] = 0
for i in range(K):
    for j in range(i):
        dp[i][i] = min(dp[i][i], dp[i][j] + B)

    di = divisors_of_N[i]
    NG = []
    for c in C:
        if c % di == 0:
            NG.append(c)

    for j in range(i+1, K):
        dj = divisors_of_N[j]
        if dj % di != 0:
            continue
        if bisect.bisect_right(NG, dj) - bisect.bisect_left(NG, di) > 0:
            break
        dp[j][i] = min(dp[j][i], dp[i][i] + (dj - di) // di * A)


ans = min(dp[K-1])
if ans >= inf:
    ans = -1
print(ans)