#include<fstream>
#include<vector>
#define MAX 100000
using namespace std;
ifstream cin("dfs.in");
ofstream cout("dfs.out");
vector<int> g[MAX+1];
int vis[MAX+1];
void dfs(int x){
    vis[x]=1;
    for(int next:g[x]){
        if(!vis[next]) dfs(next);
    }
}

int main(){
    int n,m;
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int x,y;
        cin>>x>>y;
        g[x].push_back(y);
    }
    int counter=0;
    for(int i=1;i<=n;i++){
        if(!vis[i]){
            counter++;
            dfs(i);
        }
    }
    cout<<counter;
}