#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
#define dim 8191

int n,m;
bool come[dim*2+4],go[dim*2+4],seen[dim*2+4];
vector<int> Adj[dim+2];
int L[dim*2+4],R[dim*2+4];

bool cuplaj(int x)
{
    if(seen[x]) return
        false;
    seen[x] = 1;

    for(auto p: Adj[x]) {
        if(!L[p] || cuplaj(p)) {
            R[x] = p;
            L[p] = x;
            return true;
        }
    }

    return false;
}

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

    fin >> n >> m;

    int a,b;
    for(int i = 1; i <= m; i++) {
        fin >> a >> b;
        Adj[a].push_back(b+n);
        go[a] = true;
        come[b] = true;
    }

    int Sol = 2*n;
    int C = 0;
    bool ok = true;

    while(ok) {
        ok = false;
        for(int i = 1; i <= 2*n; i++)
            seen[i] = false;

        for(int i = 1; i <= n; i++) {
            if(!R[i] && cuplaj(i)) {
                --Sol;
                ok = true;
            }
        }
    }

    fout << Sol << "\n";

}