//my G3
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <cmath>
#include <iomanip>
#include <fstream>


using namespace std;

typedef long long ll;
typedef long double ld;

typedef pair<ll, ll> Pair;
vector<vector<int>> g;
vector<vector<int>> grev;
vector<bool> been;
vector<int> cond;

vector<vector<int>> nw;
void dfsSet(int v) {
    if(been[v]) {
        return;
    }
    been[v] = true;
    for(int i = 0; i < g[v].size(); i++) {

        dfsSet(g[v][i]);
    }
    cond.push_back(v);
}

int color = 0;
vector<int> cc;
void dfs(int v) {
    if(been[v]) return;
    been[v] = true;
    cc[v] = color;
    for(int i = 0; i < grev[v].size(); i++) {
        dfs(grev[v][i]);

    }
}
set<pair<int, int>> e;
vector<pair<int, int>> ev;
void dfs2(int v) {
    if(been[v]) return;
    been[v] = true;
    for(int i = 0; i < g[v].size(); i++) {
        int a = cc[v];
        int b = cc[g[v][i]];
        if(e.find({a, b}) == e.end()) {
            e.insert({a, b});
            ev.push_back({a, b});
        }
        dfs2(g[v][i]);
    }
}

void dfs3(int v) {
    if(been[v]) return;
    been[v] = true;
    for(int i = 0; i < nw[v].size(); i++) {
        dfs3(nw[v][i]);
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, m;
    cin >> n >> m;
    g.resize(n);
    grev.resize(n);
    been.resize(n);
    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        grev[b].push_back(a);

    }
    for(int i = 0; i < n; i++) {
        dfsSet(i);
    }
    been.assign(n, false);
    cc.resize(n);

    reverse(cond.begin(), cond.end());
    for(int i = 0; i < n; i++) {
        if(!been[cond[i]]) {
            dfs(cond[i]);
            color++;
        }
    }
    been.assign(n, false);
    for(int i = 0; i < n; i++) {
        dfs2(i);
    }
    int ans = 0;
    set<pair<int, int>> ban;
    for(int i = 0; i < ev.size(); i++) {
        int a = ev[i].first;
        int b = ev[i].second;
        if(ban.find({a, b}) != ban.end()) continue;
        if(e.find({b, a}) == e.end()) {
            ans++;
            ban.insert({b, a});
        }
    }
    nw.resize(color);
    for(int i = 0; i < ev.size(); i++) {
        nw[ev[i].first].push_back(ev[i].second);
        nw[ev[i].second].push_back(ev[i].first);
    }
    been.assign(n, false);


    for(int i = 0; i < nw.size(); i++) {
        if(!been[i]) {
            dfs3(i);
            ans+=2;
        }
    }

    cout << ans-2 << endl;
    return 0;

}