class UnionFind:
	def __init__(self, n):
		self.n = n
		self.parents = [-1] * n
	
	def find(self, x):
		if self.parents[x] < 0:
			return x
		else:
			self.parents[x] = self.find(self.parents[x])
			return self.parents[x]
	
	def union(self, x, y):
		x = self.find(x)
		y = self.find(y)
		if x == y:
			return
		if self.parents[x] > self.parents[y]:
			x, y = y, x
		self.parents[x] += self.parents[y]
		self.parents[y] = x


n, m = map(int,input().split())
uf = UnionFind(n)
din = [0] * n
dout = [0] * n
for i in range(m):
	u, v = map(int,input().split())
	u -= 1
	v -= 1
	din[v] += 1
	dout[u] += 1
	uf.union(u, v)

tmp = []
r = set()
for i in range(n):
	tmp.append(dout[i] - din[i])
	if din[i] > 0:
		r.add(uf.find(i))

ren = len(r)

# euler graph
ans = 0
for i in range(n):
	if tmp[i] > 0:
		ans += tmp[i]
#ans = min(ans, tar)

if ans == 0:
	print(ren - 1)
	exit()

# jun euler graph
v = [0] * n
for i in range(n):
	if tmp[i] != 0:
		v[uf.find(i)] = 1

ans = ans - 1 - sum(v) + 1 + ren - 1

print(ans)