#int(input())
#map(int, input().split())
#list(map(int, input().split()))

import sys
sys.setrecursionlimit(200000)

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

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

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

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

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

d = dict()
for i in range(N):
    t = u.find(i)
    if t not in d:
        d[t] = min(abs(din[i] - dout[i]), 1)
    else:
        d[t] += min(abs(din[i] - dout[i]), 1)

# print(din)
# print(dout)

cnt = 0
f = 0
for k, x in d.items():
    if din[k] == 0 and dout[k] == 0:
        continue
    if x == 0:
        cnt += 1
    else:
        f = 1

if f == 0:
    print(cnt-1)
    exit()


e = 0
for i in range(N):
    e += max(0, din[i]-dout[i])

print(max(0, e+cnt-1))