from math import isqrt
from functools import lru_cache
n, m, a, b = map(int, input().split())
c = sorted(map(int, input().split()))
d = set()
for i in range(1, isqrt(n)+1):
    if n%i == 0: d.add(i); d.add(n//i)
d = sorted(d)
@lru_cache
def main(n):
    if n == 1: return -b
    ans = 10**18
    for v in d:
        if v >= n: break
        if n%v != 0: continue
        flag = True
        for w in c:
            if w > n: break
            if w%v == 0: flag = False; break
        if not flag: continue
        res = main(v)
        if res != -1: ans = min(ans, res+b+(n-v)//v*a)
    return ans if ans != 10**18 else -1
print(main(n))