#include <fstream>
#include <list>
#include <vector>
#include <bitset>
#define NMax 100002
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
int n,m,x,y,contor;
std::vector<int> G[NMax];
//std::bitset<NMax> viz;
bool viz[NMax];
void DFS(int x0)
{
    viz[x0] = true;
    for(int i=0;i<G[x0].size();++i)
    {
        if(!viz[G[x0][i]])
        {
            DFS(G[x0][i]);
        }
    }
}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;++i)
    {
        fin>>x>>y;
        G[x].push_back(y);
    }
    for(int i=1;i<=n;++i)
    {
        if(!viz[i])
        {
            contor++;
            DFS(i);
        }
    }
    fout<<contor;
    return 0;
}