#include<cstdio>
#include<vector>
#include<bitset>
using namespace std;
#define sh short int
#define pb push_back
#define NM 8195
bitset<NM>viz,v;
vector<sh>a[NM];
sh y,N,M,x,r[NM],l[NM],card,rez;
bool df(sh n)
{
	if (viz[n])
		return false;
	viz[n]=true;
	size_t g=a[n].size(),i;
	for (i=0; i<g; ++i)
	{
		y=a[n][i];
		if (!r[y])
		{
			l[n]=y;
			r[y]=n;
			return true;
		}
	}
	for (i=0; i<g; ++i)
	{
		y=a[n][i];
		if (!df(y))
		{
			l[n]=y;
			r[y]=n;
			return true;
		}
	}
	return false;
}
void dfs(sh n)
{
	v[n]=1;
	if (viz[n])
		++card;
	size_t g=a[n].size(),i;
	for (i=0; i<g; ++i)
	{
		y=a[n][i];
		if (v[y])
			continue;
		dfs(y);
	}
}
int main()
{
	freopen("felinare.in","r",stdin);
	freopen("felinare.out","w",stdout);
	scanf("%hd%hd",&N,&M);
	while (M--)
	{
		scanf("%hd%hd",&x,&y);
		a[x].pb(y);
	}
	bool ok=true;
	sh i;
	while(ok)
	{
		ok=false;
		viz.reset();
		for (i=1; i<=N; ++i)
			if (!l[i])
				ok|=df(i);
	}
	for (i=1; i<=N; ++i)
		a[i].clear();
	viz.reset();
	for (i=1; i<=N; ++i)
		if (r[i])
		{
			a[i].pb(l[i]);
			viz[i]=true;
		}
	for (i=1; i<=N; ++i)
	{
		if (!v[i]&&viz[i])
		{
			card=0;
			dfs(i);
			if (card==3)
				rez+=2;
			else
				rez+=card;
		}
	}
	printf("%hd\n",2*N-rez);
	return 0;
}