#include <cstdio>
#include <vector>
#define N 100005
using namespace std;

vector <int> graph[N];
int viz[N];
int n,m;
int nr = 0;
void citire()
{
    scanf("%d %d",&n,&m);
    for(int i = 0 ; i < m; i++)
    {
        int x,y;
        scanf("%d %d",&x,&y);
        graph[x].push_back(y);
    }
}

void dfs(int i)
{
    viz[i] = 1;
    for(int j = 0 ; j < graph[i].size();j++)
    {
            if(!viz[graph[i][j]])
            {
                int v = graph[i][j];
                dfs(v);
            }
    }
}

int main()
{
    freopen("dfs.in","r",stdin);
    freopen("dfs.out","w",stdout);
    citire();
    for(int i = 1 ; i <= n;i++)
    {
        if(!viz[i])
        {
            dfs(i);
            nr++;
        }
    }
    printf("%d",nr);
    return 0;
}