from collections import defaultdict

def mi():
    return map(int, input().split())

def lmi():
    return list(map(int, input().split()))

def init_defaultdict_int(a: list):
    d = defaultdict(int)
    for i in a:
        d[i] += 1
    return d

n, m = mi()
a = lmi()
d = init_defaultdict_int(a)
b = lmi()
ans = 0
for i in range(m):
    if b[i] < d[i+1]:
        ans += d[i+1] - b[i]
print(ans)