import sys
input = sys.stdin.readline

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

x=1

for b in B:
    x=x|(x<<b)

ANS=0

for a in A:
    ANS=ANS|(x<<a)

print(ANS.bit_count())