#include <stdio.h>
#include <vector>
using namespace std;
vector<int> v[100001];
bool viz[100001];
int cnt;
void dfs(int nod)
{
    viz[nod] = 1;
    int i;
    for(i=0; i<v[nod].size(); i++)
        if(viz[v[nod][i]] == 0)
            dfs(v[nod][i]);
}
int main()
{
    freopen("dfs.in","r",stdin);
    freopen("dfs.out","w",stdout);
    int a,b,n,m,i;
    scanf("%d%d",&n,&m);
    for(i=1; i<=m; i++)
    {
        scanf("%d%d",&a,&b);
        v[a].push_back(b);
    }
    for(i=1; i<=n; i++)
        if(viz[i] == 0)
        {
            dfs(i);
            cnt++;
        }
    printf("%d ",cnt);
    return 0;
}