#include <bits/stdc++.h>
using namespace std;
#define i64 int64_t
#define endl "\n"
#define all(a) a.begin(),a.end()
#define rep(n) for(int i = 0; i < (n); i++)

int overlapping_interval_scheduling_problem(vector<pair<i64, i64>> &tasks, int k) {
  sort(all(tasks), [](pair<i64, i64> &a, pair<i64, i64> &b) {
    return a.second < b.second;
  });
  multiset<i64> now;
  rep (k) now.insert(0);
  int ret = 0;
  for (pair<i64, i64> &e: tasks) {
    auto itr = now.lower_bound(e.first);
    if (itr != now.begin()) {
      itr--;
      ret++;
      now.erase(itr);
      now.insert(e.second);
    }
  }
  return ret;
}

int main() {
  int n, m;
  cin >> n >> m;
  vector<pair<i64, i64>> tasks(m);
  for (pair<i64, i64> &e: tasks) {
    i64 ld, rd;
    string lt_s, rt_s;
    cin >> ld >> lt_s >> rd >> rt_s;
    i64 lt = stoi(lt_s.substr(0, 2)) * 60 + stoi(lt_s.substr(3, 2)),
        rt = stoi(rt_s.substr(0, 2)) * 60 + stoi(rt_s.substr(3, 2));
    e = {ld * 1440 + lt, rd * 1440 + rt};
  }
  cout << overlapping_interval_scheduling_problem(tasks, n) << endl;
}