#include <bits/stdc++.h>

#define ll long long

#define N 100005

#define setIO(s) freopen(s".in","r",stdin)

using namespace std;

ll f[N];

queue<int>q;

int edges,n,m;

int in[N],out[N],hd[N],to[N<<1],nex[N<<1],mk[N];

void add(int u,int v)

{

    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v;

}

int main()

{

    int i,j;

    // setIO("input");

    scanf("%d%d",&n,&m);

    for(i=1;i<=m;++i)

    {

        int a,b;

        scanf("%d%d",&a,&b),add(b,a),++in[a],++out[b];

    }

    for(i=1;i<=n;++i)

    {

        if(in[i]==0 && out[i]!=0)

        {

            q.push(i),f[i]=1,mk[i]=1;

        }

    }

    for(;!q.empty();)

    {

        int u=q.front();q.pop();

        for(int i=hd[u];i;i=nex[i])

        {

            int v=to[i];

            f[v]+=f[u];

            --in[v];

            if(in[v]==0) q.push(v);

        }

    }

    ll ans=0;

    for(i=1;i<=n;++i)

    {

        if(out[i]==0 && !mk[i])

        {

            ans+=f[i];

        }

    }

    printf("%lld\n",ans);

    return 0;

}