#include <iostream>
#include <fstream>
#include <vector>
#define N 100010

using namespace std;

ifstream f("dfs.in");
ofstream g("dfs.out");

vector <int> A[N];
int i,j,nr=0,n,m,k,viz[N],el;
void dfs(int x)
{
    viz[x]=1;
    for(int k=0;k<A[x].size();k++)
    {
        if(viz[A[x][k]]==0)
        {
        dfs(A[x][k]);
        }
    }
}
int main()
{
    int x1,y1;
    f>>n>>k;
    for(i=1;i<=k;i++)
    {
        f>>x1>>y1;
        A[x1].push_back(y1);
    }
    for(i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            nr++;
            dfs(i);
        }
    }
    g<<nr;
}