#include <bits/stdc++.h>
#define INF 999999999
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
vector<int> g[100010];
int ctr, a, b, sursa, n, m, coada[100010], p, u, dist[100010], viz[100010];

void dfs(int nod)
{
    for(int i=0; i<g[nod].size();i++)
        if(!viz[g[nod][i]])
    {
        viz[g[nod][i]]=1;
        dfs(g[nod][i]);
    }
}

int main()
{
    fin>>n>>m;
    while(fin>>a>>b)
        g[a].push_back(b);
    for(int i=1;i<=n;i++)
        if(!viz[i])
        {
            dfs(i);
            ctr++;
        }
    fout<<ctr;
    return 0;
}