#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

template<typename T>
vector<vector<T>> vec2d(int n, int m, T v){
    return vector<vector<T>>(n, vector<T>(m, v));
}

template<typename T>
vector<vector<vector<T>>> vec3d(int n, int m, int k, T v){
    return vector<vector<vector<T>>>(n, vector<vector<T>>(m, vector<T>(k, v)));
}

template<typename T>
void print_vector(vector<T> v, char delimiter=' '){
    if(v.empty()) {
        cout << endl;
        return;
    }
    for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter;
    cout << v.back() << endl;
}

struct UnionFind {
    vector<int> data;
    UnionFind(int size) : data(size, -1) {}
    bool unionSet(int x, int y) {
        x = root(x); y = root(y);
        if (x != y) {
        if (data[y] < data[x]) swap(x, y);
        data[x] += data[y]; data[y] = x;
        }
        return x != y;
    }
    bool findSet(int x, int y) {
        return root(x) == root(y);
    }
    int root(int x) {
        return data[x] < 0 ? x : data[x] = root(data[x]);
    }
    int size(int x) {
        return -data[root(x)];
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int n, m; cin >> n >> m;
    vector<int> in(n);
    vector<int> deg(n);
    UnionFind uf(n);
    for(int i = 0; i < m; i++){
        int u, v; cin >> u >> v; u--; v--;
        uf.unionSet(u, v);
        in[u]++;
        in[v]--;
        deg[u]++;
    }
    vector<int> roots;
    for(int i = 0; i < n; i++){
        if(uf.root(i) == i) {
            if(uf.size(i) == 1 && deg[i] == 0){
                continue;
            }
            roots.push_back(i);
        }
    }
    
    vector<int> cnt(n);
    for(int i = 0; i < n; i++){
        if(in[i] > 0) cnt[uf.root(i)] += in[i];
    }
    if(roots.size() == 1){
        int r = roots[0];
        if(cnt[r] == 0) {
            cout << 0 << endl;
        }else{
            cout << cnt[r]-1 << endl;
        }
        return 0;
    }
    // cout << "===" << endl;
    // for(int r: roots) cout << cnt[r] << ' ';
    // cout << endl;
    int ans = roots.size()-1;
    for(int r: roots){
        if(cnt[r] == 0) {
            
        }else{
            ans += cnt[r]-1;
        }
    }
    cout << ans << endl;
}