#include <fstream>
#include <vector>

using namespace std;

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

int lg[200001];
vector<int>V[200001];
int n,T;
bool viz[100001];
int conexe;
void DFS(int x)
{
    int i;
    viz[x] = 1;
    for(i=0;i<lg[x];i++)
        if(viz[V[x][i]]==0)
        DFS(V[x][i]);
}
int main()
{
    int i,x,y;
    in>>n>>T;
    while(T--)
    {
        in>>x>>y;
        V[x].push_back(y);
        lg[x]++;
    }
    for(i=1;i<=n;i++)
        if(viz[i]==0)
        {
            conexe++;
            DFS(i);
        }
    out<<conexe<<'\n';
    return 0;
}