import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	public static class Range implements Comparable<Range>{
		int begin, end;
		
		public Range(int begin, int end){
			this.begin = begin;
			this.end = end;
		}
		
		public int compareTo(Range arg0){
			if(Integer.compare(this.end, arg0.end) != 0){
				return Integer.compare(this.end, arg0.end);
			}else{
				return Integer.compare(this.begin, arg0.begin);
			}
		}
	}
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int n = sc.nextInt();
		final int m = sc.nextInt();
		
		Range[] range = new Range[m];
		for(int i = 0; i < m; i++){
			final int d_in = sc.nextInt();
			final String[] hhmm_in = sc.next().split(":");
			final int hh_in = Integer.parseInt(hhmm_in[0]);
			final int mm_in = Integer.parseInt(hhmm_in[1]);
			
			final int d_out = sc.nextInt();
			final String[] hhmm_out = sc.next().split(":");
			final int hh_out = Integer.parseInt(hhmm_out[0]);
			final int mm_out = Integer.parseInt(hhmm_out[1]);
			
			final int checkin  = 60 * ((24 * d_in)  + hh_in)  + mm_in;
			final int checkout = 60 * ((24 * d_out) + hh_out) + mm_out;
			
			range[i] = new Range(checkin, checkout + 1);
		}
		
		Arrays.sort(range);
		
		int answer = 0;
		int[] checkout_time = new int[n];
		for(int i = 0; i < m; i++){
			final int begin = range[i].begin;
			final int end = range[i].end;
			
			int latest_time = -1;
			int latest_pos = -1;
			for(int j = 0; j < n; j++){
				if(checkout_time[j] <= begin){
					if(latest_time < checkout_time[j]){
						latest_time = checkout_time[j];
						latest_pos = j;
					}
				}
			}	
			
			if(latest_pos >= 0){
				checkout_time[latest_pos] = end;
				answer++;
			}
			
			//System.out.println(begin + " " + end);
			//System.out.println(Arrays.toString(checkout_time));
		}
		
		System.out.println(answer);
		
	}
}