#include <bits/stdc++.h>

using namespace std;

ifstream fin("felinare.in");
ofstream fout("felinare.out");

vector <int> v[10000];

int l[10000], r[10000];

bool viz[10005];

int ans = 0;
int n, m;

bool pairup(int node)
{
    if(viz[node] == 1)
        return false;

    viz[node] = 1;

    for(int i = 0; i < v[node].size(); i++)
        if(r[v[node][i]] == 0)
    {
        ans++;
        l[node] = v[node][i];
        r[v[node][i]] = node;

        return true;
    }

    for(int i = 0; i < v[node].size(); i++)
        if(pairup(r[v[node][i]]) != 0)
    {
        l[node] = v[node][i];
        r[v[node][i]] = node;

        return true;
    }

    return false;
}

int main()
{

    fin >> n >> m;

    for(int i = 1; i <= m; i++)
    {
        int x, y;

        fin >> x >> y;

        v[x].push_back(y);
    }

    bool ok = true;

    while(ok == true)
    {
        ok = false;

        fill(viz, viz + n + 1, 0);

        for(int i = 1; i <= n; i++)
            if(l[i] == 0)
                ok |= pairup(i);
    }

    fout << 2 * n - ans << '\n';

    return 0;
}