n,t=map(int,input().split())
L=list(map(int,input().split()))
k=int(input())
A=list(map(int,input().split()))

ans=10**6
for bit in range(2**k):
	tmp=[]
	cnt=0
	for i in range(k):
		if bit>>i&1:
			cnt+=1
			tmp.append(A[i])
	tmp=tmp[::-1]
	T=t
	now=0
	flag=1
	for i in range(n-1):
		if tmp:
		    if tmp[-1]==i:
		        tmp.pop()
		        T+=10
		T-=L[i]
		if T<=0:
			flag=0
			break
	if flag:
		ans=min(ans,cnt)
print(ans if ans<10**6 else -1)