#include <bits/stdc++.h>
#define startt ios_base::sync_with_stdio(false);cin.tie(0);
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
typedef unsigned long long ull;
typedef long long  ll;
using namespace std;
#define FOR(n) for(int i=0;i<n;i++)
#define vt vector
#define vint vector<int>
#define all(v) v.begin(), v.end()
#define sz(a) (int)a.size()
#define MOD 1000000007
#define MOD2 998244353
#define MX 1000000000
#define nax 100005
#define MXL 1000000000000000000
#define PI 3.14159265
#define pb push_back
#define pf push_front
#define sc second
#define fr first
#define int ll
#define endl '\n'
#define ld long double

vector<int> read(int n) {vector<int> a; for (int i = 0; i < n; i++) { int x; cin >> x; a.pb(x);} return a;}

vector<vint> adj;

vector<bool> nod;

void dfs(int u){
	nod[u] = true;
	for(auto x : adj[u])
	{
		if(nod[x])continue;
		nod[x] = true;
		dfs(x);
	}
}

int32_t main(){
	startt;
	freopen("dfs.in", "r", stdin);
	freopen("dfs.out", "w", stdout);
	int n, m;
	cin >> n >> m;
	for(int i = 0; i <= n; i++)
	{
		vint a;
		adj.pb(a);
	}
	for(int i = 0; i < m; i++)
	{
		int u, v;
		cin >> u >> v;
		adj[u].pb(v);
	}
	nod.assign(n+1, false);
	int ans = 0;
	for(int i = 1; i <= n; i++)
	{
		if(!nod[i])
		{
			dfs(i);
			ans++;
		}
	}
	cout << ans << endl;
}