#include<iostream>
#include<fstream>
using namespace std;
ifstream in("dfs.in");
ofstream out("dfs.out");
const int oo=100000;
struct nod{int inf;
nod*urm;};
nod*L[oo];
int n,m,viz[oo],nrc=1;

void citire(){
in>>n>>m;
int i,x,y;
nod *p;
for(i=1;i<=m;i++)
{in>>x>>y;
p=new nod;
p->inf=y;
p->urm=L[x];
L[x]=p;
}
}


void dfs(int x){
viz[x]=nrc;
nod *q;
q=L[x];
while(q){
if(!viz[q->inf]){dfs(q->inf);}
q=q->urm;
}

}


void rez(){
int x,i,g;
x=1;
do{g=0;dfs(x);
for(i=1;i<=n;i++)
if(!viz[i]){x=i;nrc++;g=1;break;}
}while(g);
out<<nrc<<"\n";
}

int main(){
citire();
rez();
in.close();
out.close();
return 0;}