#include<iostream>
#include<cstring>
#include<fstream>
#include<vector>
#define NMAX 10002
using namespace std;
ifstream fin("felinare.in");
ofstream fout("felinare.out");
int match1[NMAX],match2[NMAX],uz[NMAX];
vector<int>g[NMAX];
int n,m,e;
void read()
{
    fin>>n>>m;
    int x,y;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        g[x].push_back(y);
    }
    fin.close();
}
int match(int ind)
{
    if(uz[ind])return 0;
    uz[ind]=1;
    for(vector<int>::iterator it=g[ind].begin();it!=g[ind].end();it++)
         if(match2[*it]==0)
    {
        match1[ind]=*it;
        match2[*it]=ind;
        return 1;
    }

    for(vector<int>::iterator it=g[ind].begin();it!=g[ind].end();it++)
        if(match(match2[*it]))
    {
        match1[ind]=*it;
        match2[*it]=ind;
        return 1;
    }
    return 0;
}
int main()
{
    read();

    int stop=1;
    while(stop)
    {  memset(uz,0,sizeof(uz));
        stop=0;
        for(int i=1;i<=n;i++)
            if(!match1[i])stop+=match(i);
    }
    long  rez=0;
    for(int i=1;i<=n;i++)
        if(match1[i])rez++;
    fout<<2*n-rez;
    /*for(int i=1;i<=n;i++)
        if(match1[i])fout<<i<<" "<<match1[i]<<'\n';*/

fout.close();
return 0;
}