N, M = map(int, input().split())
U = list(map(int, input().split()))
T = list(map(int, input().split()))

S = sum(T) + 10
dp = [i == 0 for i in range(S)]
for x in T:
	for c in range(S - x - 1, -1, -1):
		dp[c + x] |= dp[c]

print(sum(any(0 <= t - U[i] < S and dp[t - U[i]] for i in range(N)) for t in range(202020)))