#include <iostream>
#include <fstream>
#include <cmath>
#include <queue>
using namespace std;

void dfs(int** a,int n,bool v[],int k)
{
    v[k]=true;
    for(int i=0;i<n;++i)
    {
        if(!v[i] and a[k][i]==1)
            dfs(a,n,v,i);
    }
}

int main()
{
    ifstream reader("dfs.in");
    ofstream writer("dfs.out");
    int n,m;
    int h;
    reader>>n>>m;
    int** a = new int*[n];
    for(int i=0;i<n;++i)
        a[i] = new int[n];
    for(int i=0;i<n;++i)
        for(int j=0;j<n;++j)
            a[i][j]=0;
    int x,y;
    for(int i=0;i<m;++i)
    {
        reader>>x>>y;
        x--;
        y--;
        a[x][y]=1;
    }
    bool v[n];
    for(int i=0;i<n;++i) v[i]=false;
    int cnt=0;
    for(int i=0;i<n;++i)
    {
        if(!v[i])
        {
            dfs(a,n,v,i);
            cnt++;
        }
    }
    writer<<cnt;
    return 0;
}