n, m = list(map(int, input().split()))
A = list(map(int, input().split()))
B = list(map(int, input().split()))
N = 10**5
dp = [0] * (N+1)
dp[0] = 1
for b in B:
    for t in range(N, b-1, -1):
        if dp[t-b]: dp[t] = 1
C = set()
for a in A:
    for b in range(N+1):
        if dp[b]: C.add(a+b)
print(len(C))