#include <bits/stdc++.h>

using namespace std;

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

const int N_MAX = 100005;
int n, m;
int viz[N_MAX];
vector<int> vec[N_MAX];
int cc;

void dfs(int nod, int color){
    if(!viz[nod])
        viz[nod] = color;
    for(auto v : vec[nod])
            if(!viz[v])
                dfs(v, color);
}

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