class UnionFind:
    def __init__(self, n):
        self.n = n
        self.par = [-1] * n
        self.group_ = n

    def find(self, x):
        if self.par[x] < 0:
            return x
        lst = []
        while self.par[x] >= 0:
            lst.append(x)
            x = self.par[x]
        for y in lst:
            self.par[y] = x
        return x

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False

        if self.par[x] > self.par[y]:
            x, y = y, x

        self.par[x] += self.par[y]
        self.par[y] = x
        self.group_ -= 1
        return True

    def size(self, x):
        return -self.par[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    @property
    def group(self):
        return self.group_


n, m = map(int, input().split())
in_ = [0] * n
out_ = [0] * n
UF = UnionFind(n)
loop = [False] * n

for _ in range(m):
    u, v = map(int, input().split())
    u -= 1
    v -= 1
    in_[v] += 1
    out_[u] += 1
    UF.unite(u, v)
    if u == v:
        loop[u] = True

tot = 0
for i, o in zip(in_, out_):
    tot += max(0, i - o)

C = [False] * n
for i in range(n):
    if in_[i] != out_[i]:
        C[UF.find(i)] = True

z = 0
for i in range(n):
    if UF.find(i) == i and not C[i] and (UF.size(i) > 1 or loop[i]):
        z += 1
        C[i] = True

if tot == 0:
    ans = z - 1
else:
    ans = tot - 1 + z
print(max(0, ans))