############################################################################################
import bisect,collections,copy,heapq,itertools,math,string,sys,queue,time,random
from decimal import Decimal
def I(): return input()
def IS(): return input().split()
def II(): return int(input())
def IIS(): return list(map(int,input().split()))
def LIIS(): return list(map(int,input().split()))

def make_divisors(n):
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1]

import math

def prime_numbers(n):
    prime = [True for i in range(n+1)]
    prime[0] = False
    prime[1] = False

    sqrt_n = math.ceil(math.sqrt(n))
    for i in range(2, sqrt_n):
        if prime[i]:
            for j in range(2*i, n+1, i):
                prime[j] = False
    numbers=[]
    for i in range(2,n+1):
        if prime[i]:
            numbers.append(i)

    return numbers

def factorization(n):
    arr = []
    temp = n
    for i in range(2, int(-(-n**0.5//1))+1):
        if temp%i==0:
            cnt=0
            while temp%i==0:
                cnt+=1
                temp //= i
            arr.append([i, cnt])
 
    if temp!=1:
        arr.append([temp, 1])
 
    if arr==[]:
        arr.append([n, 1])
 
    return arr
 
INF=float("inf")
MOD=998244353
MOD2=10**9+7
#sys.setrecursionlimit(500005)
def bit_count(x):
    return bin(x).count("1")
def yesno(f):
    if f:print("Yes")
    else:print("No")
####################################################

from collections import defaultdict


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):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())
n,m=IIS()
li=[0 for i in range(n)]
uf=UnionFind(n)
dic=collections.defaultdict(int)
for _ in range(m):
    u,v=IIS()
    li[u-1]+=1
    li[v-1]-=1
    uf.union(u-1,v-1)
    dic[uf.find(u-1)]+=1
ans=0
cnt2=0
s=uf.all_group_members()
for i in s:
    cnt=0
    for j in s[i]:
        cnt+=abs(li[j])
    if dic[uf.find(i)]:
        cnt2+=1
        ans+=max(cnt//2-1,0)
print(ans+max(cnt2-1,0))