#include <bits/stdc++.h>
using namespace std;

using int64 = long long;
using uint64 = unsigned long long;

using TimeStamp = pair<int, string>;

int main()
{
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n, m;
    cin >> n >> m;

    vector<pair<TimeStamp, TimeStamp>> reservation;
    for (int i = 0; i < m; i++)
    {
        int d, o;
        string t1, t2;
        cin >> d >> t1 >> o >> t2;

        reservation.emplace_back(TimeStamp{o, t2}, TimeStamp{d, t1});
    }
    sort(reservation.begin(), reservation.end());

    int ans = 0;
    priority_queue<TimeStamp, vector<TimeStamp>, greater<TimeStamp>> Q;

    for (auto& ts : reservation)
    {
        while (!Q.empty() and Q.top() < ts.second)
        {
            Q.pop();
        }

        if ((int)Q.size() < n)
        {
            Q.push(ts.first);
            ans++;
        }
    }
    cout << ans << endl;

    return 0;
}