#include<cstdio>

#include<cstdlib>

#include<iostream>

#include<fstream>

#include<algorithm>

#include<cstring>

#include<string>

#include<cmath>

#include<queue>

#include<stack>

#include<map>

#include<utility>

#include<set>

#include<bitset>

#include<vector>

#include<functional>

#include<deque>

#include<cctype>

#include<climits>

#include<complex>

//#include<bits/stdc++.h>适用于CF,UOJ，但不适用于poj

using namespace std;

typedef long long LL;

typedef double DB;

typedef pair<int,int> PII;

typedef complex<DB> CP;

#define mmst(a,v) memset(a,v,sizeof(a))

#define mmcy(a,b) memcpy(a,b,sizeof(a))

#define re(i,a,b)  for(i=a;i<=b;i++)

#define red(i,a,b) for(i=a;i>=b;i--)

#define fi first

#define se second

#define m_p(a,b) make_pair(a,b)

#define SF scanf

#define PF printf

#define two(k) (1<<(k))

template<class T>inline T sqr(T x){return x*x;}

template<class T>inline void upmin(T &t,T tmp){if(t>tmp)t=tmp;}

template<class T>inline void upmax(T &t,T tmp){if(t<tmp)t=tmp;}

const DB EPS=1e-;

inline int sgn(DB x){if(abs(x)<EPS)return ;return(x>)?:-;}

const DB Pi=acos(-1.0);

inline int gint()

  {

        int res=;bool neg=;char z;

        for(z=getchar();z!=EOF && z!='-' && !isdigit(z);z=getchar());

        if(z==EOF)return ;

        if(z=='-'){neg=;z=getchar();}

        for(;z!=EOF && isdigit(z);res=res*+z-'',z=getchar());

        return (neg)?-res:res;

    }

inline LL gll()

  {

      LL res=;bool neg=;char z;

        for(z=getchar();z!=EOF && z!='-' && !isdigit(z);z=getchar());

        if(z==EOF)return ;

        if(z=='-'){neg=;z=getchar();}

        for(;z!=EOF && isdigit(z);res=res*+z-'',z=getchar());

        return (neg)?-res:res;

    }

const int maxN=;

int N,M;

int mp[maxN+][maxN+];

int first[maxN+],now;

struct Tedge{int v,next;}edge[maxN*maxN+];

int ans;

inline void addedge(int u,int v)

  {

      now++;

      edge[now].v=v;

      edge[now].next=first[u];

      first[u]=now;

  }

int vis[maxN+];

int form[maxN+];

inline int DFS(int u)

  {

      int i,v;

      vis[u]=;

      for(i=first[u],v=edge[i].v;i!=-;i=edge[i].next,v=edge[i].v)

        if(!form[v] || (!vis[form[v]] && DFS(form[v])))

          {

              form[v]=u;

              return ;

          }

      return ;

  }

int main()

  {

      freopen("bzoj1143.in","r",stdin);

      freopen("bzoj1143.out","w",stdout);

      int i,j,k;

      N=gint();M=gint();

      re(i,,M){int u=gint(),v=gint();mp[u][v]=;}

      re(k,,N)re(i,,N)re(j,,N)if(i!=k && j!=k && i!=j && mp[i][k] && mp[k][j]) mp[i][j]=;

      mmst(first,-);now=-;

      re(i,,N)re(j,,N)if(mp[i][j])addedge(i,j);

      ans=;

      re(i,,N)

        {

            re(j,,N)vis[j]=;

            ans+=DFS(i);

        }

        printf("%d\n",N-ans);

        return ;

    }