import sys
sys.setrecursionlimit(10 ** 8)


N,M = map(int,input().split())
Gnum = [0] * (N + 1)

parent = list(range(N + 1))
def find(i):
    if parent[i] == i:return i
    parent[i] = find(parent[i])
    return parent[i]
def unite(i,j):
    I = find(i)
    J = find(j)
    if I == J:return False
    parent[i] = J
    parent[I] = J
    return True

for _ in range(M):
    u,v = map(int,input().split())
    Gnum[u] -= 1
    Gnum[v] += 1
    unite(u,v)

ans = 0
from collections import defaultdict
d = defaultdict(list)
s = set()
for i in range(1,N + 1):
    p = find(i)
    s.add(p)
    d[p].append(Gnum[i])
ans += len(s) - 1
for l in d.values():
    tmp = 0
    f = 0
    for u in l:
        if u > 0:
            if f == 0:
                tmp += u - 1
                f = 1
            else:
                tmp += u
    ans += tmp
print(ans)