N, K = map(int, input().split())
g0 = [0]*(N+1)
g1 = [0]*(N+1)
for _ in range(K):
    a, b = map(int, input().split())
    g0[a] += 1
    g1[b] += 1

ans = max(sum(abs(a-b) for a, b in zip(g0, g1))//2-1, 0)
print(ans)