#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream f ("felinare.in");
ofstream g ("felinare.out");
int n,m,rasp;
vector<int>adiacenta[8201];
bool viz[8201];
int st[8201],dr[20001];
bool cuplaj(int nod)
{
    if(viz[nod] == 1)
        return 0;
    viz[nod] = 1;
    for(auto x:adiacenta[nod])
    {
        if(dr[x]==0)
        {
            dr[x] = nod;
            st[nod]=x;
            return 1;
        }
    }
    for(auto x:adiacenta[nod])
    {
        if(cuplaj(dr[x]))
        {
            dr[x] = nod;
            st[nod] = x;
            return 1;
        }
    }
    return 0;
}
int main()
{
    f >> n>> m;
    for(int i = 1;i<=m;i++)
    {
        int x,y;
        f >>x >> y;
        adiacenta[x].push_back(y);
    }
    bool change = 1;
    while(change)
    {
        change = 0;
        for(int i= 1;i<=8201;i++)
        {
            viz[i] = 0;
        }
        for(int i= 1;i<=n;i++)
        {
            if(st[i] == 0)
            {
                if(cuplaj(i))
                {
                    change = 1;
                }
            }
        }
    }
    for(int i = 1;i<=n;i++)
    {
        if(st[i]!=0)
            rasp++;
    }
    rasp = 2*n-rasp;
    g << rasp;

}