n, m, a, b = map(int, input().split())
C = list(map(int, input().split()))
C.sort()

div = []
for i in range(1, int(n ** 0.5 + 1)):
    if n % i == 0:
        div.append(i)
        if i * i != n:
            div.append(n // i)

div.sort()
l = len(div)
inf = 1 << 60
mi = [inf] * l
for i in range(l):
    d = div[i]
    for c in C:
        if c % d == 0:
            mi[i] = c
            break

dp = [inf] * l
dp[0] = -b
for i, d in enumerate(div):
    x = dp[i] + b
    for j in range(i + 1, l):
        if div[j] % d != 0:
            continue
        if div[j] >= mi[i]:
            break
        dp[j] = min(dp[j], x + a * (div[j] // d - 1))
ans = dp[-1]
if ans == inf:
    ans = -1

print(ans)