#define _CRT_SECURE_NO_WARNINGS

#define debug(l) cerr<<#l<<' '<<l<<'\n';
#include "bits/stdc++.h"
using namespace std;
#define all(a) a.begin(), a.end()
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef long double ld;
vector<vector<int>> g;
vector<bool> used;
vector<int> mpair(1001, -1);
bool kuhn(int v) {
    if (used[v]) return false;
    used[v] = true;
    for (auto u : g[v]) {
        if (mpair[u] == -1 || kuhn(mpair[u])) {
            mpair[u] = v;
            return true;
        }
    }
    return false;
}
signed main() {
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    freopen("paths.in", "r", stdin);
    freopen("paths.out", "w", stdout);
    int n, m;
    cin >> n >> m;
    g.resize(n + 1);
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> v >> u;
        g[v].push_back(u);
    }
    used.resize(n + 1, false);
    for (int i = 1; i <= n; i++) {
        used.assign(n + 1, false);
        kuhn(i);
    }
    int cnt = 0;
    for (int i = 0; i < n + 1; i++) {
        if (mpair[i] != -1) {
            cnt++;
        }
    }
    cout << n - cnt << '\n';
}