#include<fstream>
#include<vector>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");
const int memorie=100001;
vector <int> vec[memorie];

int sel[memorie];

void bfs(long nod)
{
    for(long i=1;i<=n;i++)
        sol[i]=-1;
    sol[nod]=0;
    lungime=1;
    a[lungime]=nod;
    for(long i=1;i<=lungime;i++)
        for(long j=0;j<vecini[a[i]];j++)
            if(sol[vec[a[i]][j]]==-1)
            {
                a[++lungime]=vec[a[i]][j];
                sol[a[lungime]]=sol[a[i]]+1;
            }
}
}


int main(){int n,m,nr=0,a,b;
f>>n>>m;
for(int i=0;i<m;i++){
    f>>a>>b;
    vec[a].push_back(b);}

for (int i=1;i<=n;i++){
    if (sel[i]==0){
        df(i);
        nr++;
    }
}
g<<nr;
return 0;
}