#include <bits/stdc++.h>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");
int n, m, v[100];
int a[101][101];

void dfs(int k)
{
    v[k] = 1;
    for (int i = 1; i <= n; i++)
    {
        if (v[i] != 1 && a[k][i] == 1)
        {
            dfs(i);
        }
    }
}

int main()
{
    int x, y, c = 0;
    f >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        f >> x >> y;
        a[x][y] = 1;
    }
    for (int i = 1; i <= n; i++)
    {
        if (v[i] == 0)
        {
            c++;
            dfs(i);
        }
    }
    g << c;
    return 0;
}