#include <bits/stdc++.h>

using namespace std;

ifstream fin("dfs.in");
ofstream fout("dfs.out");

const int maxn = 1e5 + 5;

queue <int> q;
int d[maxn];
vector <int> v[maxn];

bool viz[maxn];

void dfs(int nod)  {
    if(viz[nod])
        continue;
    viz[nod] = 1;
    for(auto x : v[nod])  {
        dfs(x);
    }
}

int main()  {
    int n, m;
    fin >> n >> m;
    for(int i = 1;i <= m;i++)  {
        int x, y;
        fin >> x >> y;
        v[x].push_back(y);
    }
    int nr = 0;
    for(int i = 1;i <= n;i++)  {
        if(viz[i] == 0)
            dfs(i), nr++;
    }
    fout << nr;
    return 0;
}