#include<bits/stdc++.h> 
using namespace std;
int n,m;
int a[10010][10010]={0};
int b[10010]={0};

void ss(int x,int y)
{
    for(int i=1;i<=n;i++)
    {
        if(a[x][i]==1&&b[i]==0)
        {
            b[i]=y;
            ss(i,y);
        }
    }
}
int main()
{
    freopen("religion.in","r",stdin);
    freopen("religion.out","w",stdout);
    int c,d,ans,i,j;
    cin>>n>>m;
    ans=0;
    for(i=1;i<=m;i++)
    {
        cin>>d>>c;
        a[d][c]=1;
    }
    for(i=1;i<=n;i++)
    {
        if(b[i]==0)
        {
            ans++;
            b[i]=ans;
            ss(i,ans);
        }
    }
    cout<<ans;
    return 0;
}