#include <cstdio>
#include <queue>
#include <vector>
#define N 100001
using namespace std;

vector <int> G[N];
int n,viz[N],nrcomp;

void Read(){

    int m,x,y;
    freopen("dfs.in","r",stdin);

    scanf("%d%d",&n,&m);
    while (m--){
        scanf("%d%d",&x,&y);
        G[x].push_back(y);
        }
}

void Dfs(int node){

    int i;

    viz[node]=1;

    for (i=0;i<G[node].size();++i)
        if (!viz[G[node][i]]) Dfs(G[node][i]);
}

void Write(){

    int i;
    freopen("dfs.out","w",stdout);

    for (i=1;i<=n;i++)
    if (!viz[i]) {Dfs(i);nrcomp++;}

    printf("%d",nrcomp);
}
int main()
{
    Read();
    Write();
    return 0;
}