def devisors(n):
    d = []
    a = 1
    while a * a < n:
        if n % a == 0:
            d.append(a)
            d.append(n // a)
        a += 1
    if a * a == n:
        d.append(a)
    return d

INF = 10 ** 18
n, m, a, b = map(int, input().split())
c = list(map(int, input().split()))
c.sort()
dv = devisors(n)
dv.sort()
k = len(dv)
dp = [INF] * k
dp[0] = 0
prv = [-1] * k
for i in range(k):
    x = INF
    for j in range(m):
        if c[j] % dv[i] == 0:
            x = c[j]
            break
    for j in range(i + 1, k):
        if dv[j] % dv[i] > 0:
            continue
        if dv[j] >= x:
            break
        if dp[j] > dp[i] + a * (dv[j] // dv[i] - 1) + b:
            dp[j] = dp[i] + a * (dv[j] // dv[i] - 1) + b
            prv[j] = dv[i]
if dp[-1] > 10 ** 15:
    print(-1)
else:
    print(dp[-1] - b)