#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class t, class u>
void chmax(t& first, u second) {
  if (first < second) first = second;
}
template <class t, class u>
void chmin(t& first, u second) {
  if (second < first) first = second;
}
template <class t>
using vc = vector<t>;
template <class t>
using vvc = vc<vc<t>>;
using pi = pair<int, int>;
using vi = vc<int>;
template <class t, class u>
ostream& operator<<(ostream& os, const pair<t, u>& p) {
  return os << "{" << p.first << "," << p.second << "}";
}
template <class t>
ostream& operator<<(ostream& os, const vc<t>& v) {
  os << "{";
  for (auto e : v) os << e << ",";
  return os << "}";
}
using uint = unsigned;
using ull = unsigned long long;
template <class t, size_t n>
ostream& operator<<(ostream& os, const array<t, n>& first) {
  return os << vc<t>(first.begin(), first.end());
}
template <int i, class T>
void print_tuple(ostream&, const T&) {}
template <int i, class T, class H, class... Args>
void print_tuple(ostream& os, const T& t) {
  if (i) os << ",";
  os << get<i>(t);
  print_tuple<i + 1, T, Args...>(os, t);
}
template <class... Args>
ostream& operator<<(ostream& os, const tuple<Args...>& t) {
  os << "{";
  print_tuple<0, tuple<Args...>, Args...>(os, t);
  return os << "}";
}
template <class t>
void print(t x, int suc = 1) {
  cout << x;
  if (suc == 1) cout << "\n";
  if (suc == 2) cout << " ";
}
ll read() {
  ll i;
  cin >> i;
  return i;
}
vi readvi(int n, int off = 0) {
  vi v(n);
  for (int i = int(0); i < int(n); i++) v[i] = read() + off;
  return v;
}
template <class T>
void print(const vector<T>& v, int suc = 1) {
  for (int i = int(0); i < int(v.size()); i++)
    print(v[i], i == int(v.size()) - 1 ? suc : 2);
}
string readString() {
  string s;
  cin >> s;
  return s;
}
template <class T>
T sq(const T& t) {
  return t * t;
}
void yes(bool ex = true) {
  cout << "Yes"
       << "\n";
  if (ex) exit(0);
}
void no(bool ex = true) {
  cout << "No"
       << "\n";
  if (ex) exit(0);
}
void possible(bool ex = true) {
  cout << "Possible"
       << "\n";
  if (ex) exit(0);
}
void impossible(bool ex = true) {
  cout << "Impossible"
       << "\n";
  if (ex) exit(0);
}
constexpr ll ten(int n) { return n == 0 ? 1 : ten(n - 1) * 10; }
const ll infLL = LLONG_MAX / 3;
const int inf = INT_MAX / 2 - 100;
int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
int topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
int botbit(signed first) { return first == 0 ? 32 : __builtin_ctz(first); }
int botbit(ll first) { return first == 0 ? 64 : __builtin_ctzll(first); }
int popcount(signed t) { return __builtin_popcount(t); }
int popcount(ll t) { return __builtin_popcountll(t); }
bool ispow2(int i) { return i && (i & -i) == i; }
ll mask(int i) { return (ll(1) << i) - 1; }
bool inc(int first, int second, int c) {
  return first <= second && second <= c;
}
template <class t>
void mkuni(vc<t>& v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
ll rand_int(ll l, ll r) {
  static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());
  return uniform_int_distribution<ll>(l, r)(gen);
}
template <class t>
void myshuffle(vc<t>& first) {
  for (int i = int(0); i < int(int(first.size())); i++)
    swap(first[i], first[rand_int(0, i)]);
}
template <class t>
int lwb(const vc<t>& v, const t& first) {
  return lower_bound(v.begin(), v.end(), first) - v.begin();
}
template <class d>
struct maxflow {
  struct E {
    int to, rev;
    d cap;
  };
  vvc<E> g;
  vi itr, lv, q;
  maxflow(int n) : g(n), itr(n), lv(n), q(n) {}
  void ae(int s, int t, d c) {
    g[s].push_back({t, (int)g[t].size(), c});
    g[t].push_back({s, (int)g[s].size() - 1, 0});
  }
  void bfs(int s) {
    fill(lv.begin(), lv.end(), -1);
    lv[s] = 0;
    int l = 0, r = 0;
    q[r++] = s;
    while (l < r) {
      int v = q[l++];
      for (auto e : g[v])
        if (e.cap > 0 && lv[e.to] == -1) {
          lv[e.to] = lv[v] + 1;
          q[r++] = e.to;
        }
    }
  }
  d dfs(int v, int t, d f) {
    if (v == t) return f;
    d res = 0;
    for (int& i = itr[v]; i < (int)g[v].size(); i++) {
      E& e = g[v][i];
      if (e.cap > 0 && lv[e.to] == lv[v] + 1) {
        d first = dfs(e.to, t, min(f, e.cap));
        if (first > 0) {
          e.cap -= first;
          g[e.to][e.rev].cap += first;
          res += first;
          f -= first;
          if (f <= 0) break;
        }
      }
    }
    return res;
  }
  d calc(int s, int t) {
    d f = 0;
    while (1) {
      bfs(s);
      if (lv[t] == -1) return f;
      fill(itr.begin(), itr.end(), 0);
      f += dfs(s, t, inf);
    }
  }
};
const int smax = 1 << 15;
int idx[smax], tmp[smax];
int head;
vc<pi> es;
void upd(int i) {
  for (int k = int(0); k < int(2); k++)
    if (idx[i * 2 + k] == -1) {
      idx[i] = idx[i * 2 + 1 - k];
      return;
    }
  idx[i] = head++;
  for (int k = int(0); k < int(2); k++)
    if (idx[i * 2 + k] != -1) es.emplace_back(idx[i], idx[i * 2 + k]);
}
void add(int second, int e, int l, int r, int i) {
  if (e <= l || r <= second) return;
  if (second <= l && r <= e) {
    idx[i] = tmp[i];
    return;
  }
  int m = (l + r) / 2;
  add(second, e, l, m, i * 2);
  add(second, e, m, r, i * 2 + 1);
  upd(i);
}
void del(int second, int e, int l, int r, int i) {
  if (e <= l || r <= second) return;
  if (second <= l && r <= e) {
    tmp[i] = idx[i];
    idx[i] = -1;
    return;
  }
  int m = (l + r) / 2;
  del(second, e, l, m, i * 2);
  del(second, e, m, r, i * 2 + 1);
  upd(i);
}
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  int n;
  cin >> n;
  int s = 1;
  while (s < n) s *= 2;
  memset(idx, -1, sizeof(idx));
  head = 2;
  for (int i = int(0); i < int(n); i++) idx[s + i] = head++;
  for (int i = int(s) - 1; i >= int(1); i--) upd(i);
  int q;
  cin >> q;
  vvc<pi> addq(n + 1), delq(n + 1);
  for (int _ = int(0); _ < int(q); _++) {
    int first, second, c, d;
    cin >> first >> second >> c >> d;
    first--;
    second--;
    delq[first].emplace_back(second, d);
    addq[c].emplace_back(second, d);
  }
  vi z;
  for (int i = int(0); i < int(n); i++) {
    for (auto lr : addq[i]) {
      add(lr.first, lr.second, 0, s, 1);
    }
    for (auto lr : delq[i]) {
      del(lr.first, lr.second, 0, s, 1);
    }
    z.push_back(idx[1]);
  }
  maxflow<int> mf(head);
  for (auto i : z)
    if (i != -1) mf.ae(0, i, 1);
  for (int i = int(0); i < int(n); i++) mf.ae(2 + i, 1, 1);
  for (auto e : es) {
    mf.ae(e.first, e.second, inf);
  }
  int f = mf.calc(0, 1);
  print(f);
}
