#include<bits/stdc++.h>
#include<atcoder/all>
using namespace atcoder;
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
using ll=long long;
using ld=long double;
using ull=unsigned long long;
using i128 = __int128_t;
#define vs vector<string>
#define rep(i,n) for(ll i=0;i<ll(n);i++)
#define rep2(i,n) for(ll i=n-1;i>=0;i--)
#define rep3(i,a,b) for(ll i=a;i<=ll(b);i++)
#define rep4(i,a,b) for(ll i=a;i>=ll(b);i--)
#define forv(i,V) for(const auto& i:V)
#define all(x) x.begin(),x.end()
#define fi first
#define se second
#define SIZE(x) int(x.size())
constexpr ll mod=998244353;
//constexpr ll mod=1000000007;
#define pi 3.14159265358979323
#define INF32 2147483647
#define INF64 9223372036854775807
#define faster ios::sync_with_stdio(false);std::cin.tie(nullptr)
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define rev reverse
#define vi vector<int>
#define vll vector<ll>
#define vpi vector<pair<int,int>>
#define vpll vector<pair<ll,ll>>
#define vvi vector<vector<int>>
#define vvll vector<vector<ll>>
#define prq priority_queue
#define lb lower_bound
#define ub upper_bound
#define popcnt __builtin_popcountll
#define TLE while(true);
#define RE assert(false);
#define MLE vector<vector<vector<long long>>> mle_mle(400,vector<vector<long long>>(1000,vector<long long>(1000)));
const string YESNO[2] = {"NO", "YES"};
const string YesNo[2] = {"No", "Yes"};
const string yesno[2] = {"no", "yes"};
#define rall(n) (n).rbegin(),(n).rend()
#define INT(...) int __VA_ARGS__;scan(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;scan(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;scan(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__;scan(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__;scan(__VA_ARGS__)
#define LD(...) ld __VA_ARGS__;scan(__VA_ARGS__)
template<typename T,typename U>
ostream &operator<<(ostream&os,const pair<T,U>&p){os<<p.first<<" "<<p.second;return os;}
template<typename T,typename U>
istream &operator>>(istream&is,pair<T,U>&p){is>>p.first>>p.second;return is;}
template<typename T>
ostream &operator<<(ostream&os,const vector<T>&v){for(auto it=v.begin();it!=v.end();){os<<*it<<((++it)!=v.end()?" ":"");}return os;}
template<typename T>
istream &operator>>(istream&is,vector<T>&v){for(T &in:v){is>>in;}return is;}
void scan(){}
template<class Head,class... Tail>
void scan(Head&head,Tail&... tail){cin>>head;scan(tail...);}
template<class T>
void print(const T &t){cout<<t<<'\n';}
template<class Head, class... Tail>
void print(const Head &head, const Tail &... tail){cout<<head<<' ';print(tail...);}
template<class... T>
void fin(const T &... a){print(a...);exit(0);}
ll max(int a,ll b){return max((ll)a,b);}
ll max(ll a,int b){return max((ll)b,a);}
ll min(int a,ll b){return min((ll)a,b);}
ll min(ll a,int b){return min((ll)b,a);}
//a以上b以下の個数
template<typename T>
ll RangeOK(ll a,ll b,vector<T> &v){
  return max(ub(all(v),b)-lb(all(v),a),0);
}
template <typename T>
vector<T> compress(vector<T> &X) {
    vector<T> vals = X;
    sort(vals.begin(), vals.end());
    vals.erase(unique(vals.begin(), vals.end()), vals.end());
    for (int i = 0; i < (int)X.size(); i++) {
        X[i] = lower_bound(vals.begin(), vals.end(), X[i]) - vals.begin();
    }
    return vals;
}
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
*/
#ifndef ATCODER_DSU_HPP
#define ATCODER_DSU_HPP 1

#include <algorithm>
#include <cassert>
#include <vector>

namespace atcoder {

// Implement (union by size) + (path compression)
// Reference:
// Zvi Galil and Giuseppe F. Italiano,
// Data structures and algorithms for disjoint set union problems
struct dsu {
  public:
    dsu() : _n(0) {}
    explicit dsu(int n) : _n(n), parent_or_size(n, -1) {}

    int merge(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        int x = leader(a), y = leader(b);
        if (x == y) return x;
        if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y);
        parent_or_size[x] += parent_or_size[y];
        parent_or_size[y] = x;
        return x;
    }

    bool same(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        return leader(a) == leader(b);
    }

    int leader(int a) {
        assert(0 <= a && a < _n);
        if (parent_or_size[a] < 0) return a;
        return parent_or_size[a] = leader(parent_or_size[a]);
    }

    int size(int a) {
        assert(0 <= a && a < _n);
        return -parent_or_size[leader(a)];
    }

    std::vector<std::vector<int>> groups() {
        std::vector<int> leader_buf(_n), group_size(_n);
        for (int i = 0; i < _n; i++) {
            leader_buf[i] = leader(i);
            group_size[leader_buf[i]]++;
        }
        std::vector<std::vector<int>> result(_n);
        for (int i = 0; i < _n; i++) {
            result[i].reserve(group_size[i]);
        }
        for (int i = 0; i < _n; i++) {
            result[leader_buf[i]].push_back(i);
        }
        result.erase(
            std::remove_if(result.begin(), result.end(),
                           [&](const std::vector<int>& v) { return v.empty(); }),
            result.end());
        return result;
    }

  private:
    int _n;
    // root node: -1 * component size
    // otherwise: parent
    std::vector<int> parent_or_size;
};

}  // namespace atcoder

#endif  // ATCODER_DSU_HPP
using namespace atcoder;
int main(){
  INT(n, m);
  vvll deg(n, vll(2));
  dsu d(n);
  vll seen(n);
  rep(i, m){
    LL(a, b);
    a--, b--;
    d.merge(a, b);
    deg[a][0]++;
    deg[b][1]++;
    seen[a] = 1;
    seen[b] = 1;
  }
  auto g2 = d.groups();
  vvi g;
  rep(i, g2.size()){
    if(g2[i].size() != 1 || seen[g2[i][0]]) g.pb(g2[i]);
  }
  ll ans = g.size()-1;
  rep(i, g.size()){
    vll p;
    for(auto x:g[i]) p.pb(abs(deg[x][0]-deg[x][1]));
    sort(all(p));
    ll sum = 0;
    for(auto x:p) sum += x;
    if(sum != 0) ans += sum/2-1;
  }
  fin(ans);
}