#include <bits/stdc++.h>

using namespace std;

ifstream inf("dfs.in");
ofstream outf("dfs.out");

int n, m;
vector<int> vec[100010];
bool vis[100010];
int sol;

void DFS()
{
    for(int i=1; i<=n; i++)
    {
        if(vis[i])
            continue;
        int st=i;
        sol++;
        queue<int> q;
        q.push(st);
        while(!q.empty())
        {
            int cn=q.front();
            q.pop();
            vis[cn]=true;
            for(auto it:vec[cn])
                if(!vis[it])
                    q.push(it);
        }
    }
    outf<<sol;
}

int main()
{
    inf>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int x,y;
        inf>>x>>y;
        vec[x].push_back(y);
    }

    DFS();

    return 0;
}