#include<bits/stdc++.h>
#define debug(x) cerr << #x << " " << x << "\n"
#define debugs(x) cerr << #x << " " << x << " "
#pragma GCC optimize("Ofast")
#define int long long

using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int range_rng(int l, int r)
{
    return uniform_int_distribution<int>(l,r)(rng);
}

vector<int> nodes[20005];
map<int,int> mvc;
int match[20005];
bool visited[20005];

bool path(int node)
{
    int nxt;
    visited[node]=1;
    for (auto x : nodes[node])
    {
         nxt=match[x];
         if (nxt)
         {
             if (!visited[nxt] && path(nxt))
             {
                 match[x]=node;
                 match[node]=x;
                 return 1;
             }
         }
         else
         {
             match[node]=x;
             match[x]=node;
             return 1;
         }
    }
    return 0;
}

signed main()
{
    ifstream fin("felinare.in");
    ofstream fout("felinare.out");
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,m,i,j,u,v,cuplaj;
    bool ok;
    fin >> n >> m;
    for (i=1;i<=m;i++)
    {
         fin >> u >> v;
         nodes[u].push_back(v+n);
         nodes[v+n].push_back(u);
    }
    for (i=1;i<=n*2;i++)
         match[i]=0;
    ok=1;
    cuplaj=0;
    while (ok)
    {
        ok=0;
        for (i=1;i<=n*2;i++)
             visited[i]=0;
        for (i=1;i<=n;i++)
        {
             if (!match[i] && !visited[i] && path(i))
             {
                 ok=1;
                 cuplaj++;
             }
        }
    }
    fout << n*2-cuplaj;
    return 0;
}