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

g = [ [] for _ in range(2*N)]
for _ in range(M):
    a,b = list(map(int, input().split()))
    
    g[a-1].append(b-1)
    g[b-1].append(a-1)

relation_cnt = []

for i in range(2*N):
    relation_cnt.append([i, len(g[i])])
relation_cnt.sort(key=lambda x:x[1])
paired = set()
for i in range(2*N):
    node, cnt = relation_cnt[i]
    for node2 in g[node]:
        if node2 in paired or node in paired :
            continue
        paired.add(node)
        paired.add(node2)
# print(paired)
print((2*N - len(paired))//2)