import java.util.*;

public class Run {
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        scan.useDelimiter("[^0-9]");
        int N = scan.nextInt();
        if (N < 1||N > 30) System.exit(1);
        int hsum = 0;
        int msum = 0;
        for (int i = 0; i < N; i++) {
            int H = scan.nextInt();
            int M = scan.nextInt();
            int h = scan.nextInt();
            int m = scan.nextInt();
            hsum += (h - H + 24)%24;
            msum += m - M;
            if (msum > 59) {
                hsum++;
                msum -= 60;
            } else if (msum < 0) {
                hsum--;
                msum += 60;
            }
        }
        System.out.println(hsum*60 + msum);
    }
}