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

INF = 1<<60

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

div = sorted(divisor(N))
L = len(div)
dp = [INF]*L
dp[0] = 0
for i in range(L-1):
    idx = 0
    NG = False
    for j in range(i+1, L):
        while idx < M and C[idx] <= div[j]:
            if div[i] <= C[idx] and C[idx]%div[i] == 0:
                NG = True
            idx += 1
        if NG: break
        if div[j]%div[i] != 0: continue
        dp[j] = min(dp[j], dp[i]+A*(div[j]//div[i]-1)+B)

print(dp[-1]-B if dp[-1] != INF else -1)