#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>> tasks;
    for (int i = 0; i < m; i++)
    {
        int d, o;
        string t1, t2;
        cin >> d >> t1 >> o >> t2;

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

    int ans = 0, cnt = 0;
    vector<bool> used(m, false);
    for (int i = 0; i < m; i++)
    {
        int target = -1;
        for (int j = 0; j < i; j++)
        {
            if (used[j] and tasks[j].first < tasks[i].second and
                    (target < 0 or tasks[target].first < tasks[j].first))
            {
                target = j;
            }
        }
        if (target >= 0)
        {
            used[target] = false;
            cnt--;
        }

        if (cnt < n)
        {
            used[i] = true;
            cnt++;
            ans++;
        }
    }
    cout << ans << endl;

    return 0;
}