import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.parseInt(scan.nextLine());
		String []s = new String[N];
		for(int i = 0; i < N; i++) {
			s[i] = scan.nextLine();
		}
		scan.close();
		int ans = 0;
		for(int i = 0; i < N; i++) {
			String []str = s[i].split("[ :]");
			int H = Integer.parseInt(str[0]);
			int M = Integer.parseInt(str[1]);
			int h = Integer.parseInt(str[2]);
			int m = Integer.parseInt(str[3]);
			int start = H * 60 + M;
			int end = h * 60 + m;
			int k = end -start;
			if(k < 0) {
				ans += 24 * 60 + k;
			}else if(k > 0) {
				ans += k;
			}else {
				ans += 24 * 60;
			}
		}
		System.out.println(ans);
	}
}