#include <iostream>
#include<stdio.h>
#include<vector>
 using namespace std;
vector <int>  g[100005],gt[100005];
int n,m,viz1[100005],viz2[100005],viz3[100005];

void citire()
{int x,y;
    freopen("ctc.in","r",stdin);
    scanf("%d %d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        g[x].push_back(y);
        gt[y].push_back(x);

    }
}
void dfsg(int x)
{int i;
viz1[x]=1;
for(i=0;i<g[x].size();++i)
if (viz1[g[x][i]]==0) dfsg(g[x][i]);
}
void dfsgt(int x)
{int i;
viz2[x]=viz1[x]+1;
for(i=0;i<gt[x].size();++i)
if (viz1[gt[x][i]]==0) dfsgt(gt[x][i]);
}
 int main()
 {int nr;
    citire();
    for(int i=1;i<=n;++i)
        if (viz3[i]==0)
        {
        dfsg(i);
        dfsgt(i);
        ++nr;

        }
        cout<<nr;
        freopen("ctc.out","w",stdout);
     return 0;
}