#include <bits/stdc++.h>
using namespace std;
vector<int> adj[100000];
bool visited[1000000];
int n,m,x,y,cnt=0;

void dfs(int s) {
if (visited[s]) return;
visited[s] = true;
for (auto u: adj[s]) {
dfs(u);
}
}

int main(){
freopen("dfs.in","r",stdin);
freopen("dfs.out","w",stdout);
cin >> n >> m;
for(int i=1; i<=m; i++){
    cin >> x >> y;
    adj[x].push_back(y);
}
for(int j=1; j<=n; j++){
    if(!visited[j]){
            dfs(j);
            cnt++;
         }
}
cout << cnt;
}