using namespace std;

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <iostream>
#include <cmath>
#include <cassert>
#include <deque>
#include <ctime>
#define NDEBUG

#define FIN "felinare.in"
#define FOUT "felinare.out"

#define maxn 20000


#ifndef NDEBUG
int stp;
#endif

struct nod { short x, poz; bool cap; nod(){};  nod(short a, short b, bool c){x=a; poz=b; cap=c;};};

vector<vector<nod> > x;

int n, m, E;
short int source, sink;
//int t[maxn<<1];
short int d[maxn<<1];
bool Viz[maxn<<1];
int bfs();
void solve();

void read()
{

	int i,p, q;
		scanf("%d %d\n", &n, &m);

		source=0;
		sink=n+n+1;
		x.resize(n+n+2);
		//poz.resize(n+n+2);
		for(i=0;i<m;++i)
		{
			scanf("%d %d\n", &p, &q);  
			x[p].push_back(nod(q+n, x[q+n].size(), 1));
			x[q+n].push_back(nod(p, x[p].size()-1, 0));
		}
		for(i=1;i<=n;++i)
		  {
		    x[source].push_back(nod(i, x[i].size(), 1));
		    x[i].push_back(nod(source, x[source].size()-1, 0));
		  }		    
		for(i=n+1;i<sink;++i) 
		  {
		    x[i].push_back(nod(sink, x[sink].size(), 1));
		    x[sink].push_back(nod(i, x[i].size()-1, 0));
		  }
}


int bfs()
{
	short Q[maxn<<1], p=1, q=1;
	bool viz[maxn<<1];
		
	memset(viz, 0,sizeof(viz));
	//memset(t, -1, sizeof(t));
	memset(d, 0, sizeof(d));
	viz[source]=1;
	Q[1]=source;
	d[1]=0;
	int u;
	short i, j;
	vector<nod>::iterator it,jt, xu;
	
	while(p<=q)
	{
		u=Q[p++];
		xu=x[u].end();
		for(it=x[u].begin() ;it!=xu;++it)
		{
		 i=it->x; 
		  if(!viz[i]&& (it->cap)) //(aa[u][(i)>>3]&(1<<((i)&7))))
			{
				viz[i]=1;
				d[i]=d[u]+1;
				Q[++q]=i;
			       
			}
		}
	}
	
	return d[sink];
}



int flow, ok=1, dsink,nr;
int counter;

void DFS(short nd, short nr)
{
  //printf("%d %d\n", nd, nr);
  if(nr>dsink) return;
  if(nd==sink) { ++flow; ok=0; return ;}
  Viz[nd]=1;
  vector<nod>::iterator it;
  
  for(it=x[nd].begin();it!=x[nd].end();++it)
    if(nr==d[it->x]-1)
     {
      
       if( ok && !Viz[it->x] && (it->cap) )   //(aa[nd][i>>3]&(1<<(i&7))))//a[nd][i])
	{
	  //++nr;
	  DFS(it->x, nr+1);
	  //--nr;
	  if(!ok)
	    {
	     	it->cap=0;
		x[it->x][it->poz].cap=1;
		if(nd==source) ok=1;
		else break;
	    }
	}
     }
}


void solve()
{
	int i, j;
	int p;
	
	flow=0;
	
	while(dsink=bfs())
	{	
	 
	  memset(Viz, 0, sizeof(Viz));
	  ok=1;
	  nr=0;
	 
	  DFS(source, 0);
	 
		
      	}
	printf("%d\n", 2*n-flow);
	
}


int main()
{
  //freopen("fel.in", "r", stdin);
  freopen(FIN, "r", stdin);
	
    	freopen(FOUT, "w", stdout);
  
	read();
	solve();
       
	
	
	return 0;
}