#include <iostream>
#include <iomanip>
#include <cstdio>
#include <queue>
#include <cstring>
#include <vector>
#include <map>
#include <algorithm>
#include <cctype>
#include <cmath>
#include <bitset>
#include <set>
#include <deque>
#include <stack>
#include <atcoder/all>
#include <array>
using namespace std;
#define rep(i,n) for(int i = 0; i < (int)(n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < (t); ++i)
#define dsrep(i,t,s) for(int i = (t)-1; i >= (s); --i)
#define rng(a) a.begin(),a.end()
#define rrng(a) a.rbegin(),a.rend()
#define isin(x,l,r) ((l) <= (x) && (x) < (r))
int dx4[4]={1,0,-1,0};
int dy4[4]={0,-1,0,1};
using ll = long long;
using uint = unsigned;
using ull = unsigned long long;
using P = pair<int,int>;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
// const ll mod = 998244353;
const ll mod = 1e9 + 7;

///////////////////////////////////////////
int n, m;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  cin >> n >> m;
  vector<P> a(m);
  rep(i, m) {
    int l, r;
    cin >> l >> r;
    a[i] = {r, l};
  }
  sort(a.begin(), a.end());

  vector<int> check;
  rep(i, m) {
    auto [r, l] = a[i];
    auto it = lower_bound(check.begin(), check.end(), l);

    if(it == check.end()) check.push_back(r);
  }

  cout << n - check.size() << endl;
}