import sys
input = sys.stdin.readline
from collections import defaultdict
class UnionFind:
    def __init__(self, n:int):
        self.n = n
        self.parents = [-1] * n
    def find(self, x:int):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
    def union(self, x:int, y:int):
        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:int):
        return -self.parents[self.find(x)]
    def same(self, x:int, y:int):
        return self.find(x) == self.find(y)
    def group_count(self):
        return len(self.roots())
    def all_group_members(self):
        members = defaultdict(list)
        for i in range(self.n): members[self.find(i)].append(i)
        return members


N,M=map(int,input().split())
uf = UnionFind(N)
dif = [0]*N
loop = [0]*N
for _ in range(M):
    u,v=map(lambda x:int(x)-1,input().split())
    if u==v:
        loop[u]=1
        continue
    dif[u]+=1
    dif[v]-=1
    uf.union(u,v)
# グループごとに計算
members = uf.all_group_members()
ans_list = []
for member in members.values():
    if len(member)==1 and loop[member[0]]==0:continue
    x=sum([abs(dif[m]) for m in member])//2
    if x:
        x-=1
    ans_list.append(x)
ans_list.sort()
# 0は他と接続コスト必要
ans = sum(ans_list)
if ans==0:
    ans = len(ans_list)-1
else:
    zero = 0
    one = 0
    tmp=[]
    for a in ans_list:
        if a==0:
            zero+=1
        elif a==1:
            one += 1
        else:
            tmp.append(a)
    # 1は2以上とつなぐ
    tmp.sort()
    for a in tmp:
        d = min(a-1,one)
        one -= d
        if a-d==1:
            one+=1
    ans += one//2
    if one:
        zero+=1
    ans += zero-1


print(ans)