#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5, M = 4e5 + 5;
const int INF = 0x3f3f3f3f;
struct node {
  int x, l, r, f;
  node() {}
  node(int _x, int _l, int _r, int _f) : x(_x), l(_l), r(_r), f(_f) {}
} line[2 * N];
bool cmp(node a, node b) {
  if (a.x != b.x) return a.x < b.x;
  return a.f < b.f;
}
struct mode {
  int l, r;
} tree[N * 8];
int rt1, rt2, tcnt;
struct lode {
  int u, v, cap, nxt;
} edge[M * 8];
int head[M], mcnt = 1;
int S, T;
int a[N];
int n, m;
void add_edge(int u, int v, int cap) {
  mcnt++;
  edge[mcnt].u = u;
  edge[mcnt].v = v;
  edge[mcnt].cap = cap;
  edge[mcnt].nxt = head[u];
  head[u] = mcnt;
}
void add(int u, int v, int cap) {
  add_edge(u, v, cap);
  add_edge(v, u, 0);
}
void Build(int &x, int fa, int l, int r, int dir) {
  x = ++tcnt;
  if (fa) {
    if (!dir)
      add(x, fa, INF);
    else
      add(fa, x, INF);
  }
  if (l == r) return;
  int mid = (l + r) >> 1;
  Build(tree[x].l, x, l, mid, dir);
  Build(tree[x].r, x, mid + 1, r, dir);
}
void Build2(int x, int l, int r, int dir) {
  if (l == r) {
    if (dir)
      add(S, x, 1);
    else
      add(x, T, 1);
    return;
  }
  int mid = (l + r) >> 1;
  Build2(tree[x].l, l, mid, dir);
  Build2(tree[x].r, mid + 1, r, dir);
}
void Query(int x, int l, int r, int pl, int pr, int y, int dir) {
  if (pl > pr || x == 0) return;
  if (pl <= l && r <= pr) {
    if (!dir)
      add(x, y, INF);
    else
      add(y, x, INF);
    return;
  }
  int mid = (l + r) >> 1;
  if (pl <= mid) Query(tree[x].l, l, mid, pl, pr, y, dir);
  if (pr > mid) Query(tree[x].r, mid + 1, r, pl, pr, y, dir);
}
void Insert(int x, int l, int r) {
  int pos = -1, last = -1, y;
  for (int i = l; i <= r + 1; i++) {
    if (i <= r) y = a[i] + 1, a[i] = -1;
    if (y != last || i == r + 1) {
      if (pos != -1) {
        int z = ++tcnt;
        Query(rt1, 1, n, pos, i - 1, z, 0);
        Query(rt2, 1, n, last, x, z, 1);
      }
      pos = i;
      last = y;
    }
  }
}
void Update(int x, int l, int r) {
  for (int i = l; i <= r; i++) a[i] = x;
}
int dist[M];
int cur[M];
queue<int> q;
bool bfs() {
  for (int i = 1; i <= tcnt; i++) dist[i] = -1, cur[i] = head[i];
  dist[S] = 0;
  q.push(S);
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    for (int i = head[u]; i; i = edge[i].nxt) {
      int v = edge[i].v;
      if (~dist[v] || !edge[i].cap) continue;
      dist[v] = dist[u] + 1;
      q.push(v);
    }
  }
  return ~dist[T];
}
int dfs(int u, int CAP) {
  if (u == T || !CAP) return CAP;
  int flow = 0;
  for (int &i = cur[u]; i; i = edge[i].nxt) {
    int v = edge[i].v, cap = edge[i].cap;
    if (dist[v] == dist[u] + 1 && cap) {
      int f = dfs(v, min(cap, CAP));
      if (!f) continue;
      flow += f;
      CAP -= f;
      if (edge[i].cap != INF) edge[i].cap -= f;
      if (edge[i ^ 1].cap != INF) edge[i ^ 1].cap += f;
      if (!CAP) break;
    }
  }
  return flow;
}
int Dinic() {
  int max_flow = 0;
  while (bfs()) {
    max_flow += dfs(S, INF);
  }
  return max_flow;
}
void Read(int &x) {
  x = 0;
  char c = getchar();
  while (c < '0' || c > '9') c = getchar();
  while (c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
}
int main() {
  Read(n), Read(m);
  Build(rt1, 0, 1, n, 0);
  Build(rt2, 0, 1, n, 1);
  for (int i = 1; i <= m; i++) {
    int l, d, u, r;
    Read(l), Read(d), Read(r), Read(u);
    line[i] = node(l - 1, d, u, 1);
    line[i + m] = node(r, d, u, -1);
  }
  sort(line + 1, line + m * 2 + 1, cmp);
  for (int i = 1; i <= 2 * m; i++) {
    if (line[i].f == 1)
      Insert(line[i].x, line[i].l, line[i].r);
    else
      Update(line[i].x, line[i].l, line[i].r);
  }
  Insert(n, 1, n);
  S = ++tcnt;
  T = ++tcnt;
  Build2(rt1, 1, n, 1);
  Build2(rt2, 1, n, 0);
  int ans = Dinic();
  printf("%d\n", ans);
}
