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 msum = 0;
        int ans = 0;
        for (int i = 0; i < N; i++) {
            int H = scan.nextInt();
            int M = scan.nextInt();
            int h = scan.nextInt();
            int m = scan.nextInt();
            msum = m - M;
            if (msum > 59) {
                h++;
                msum -= 60;
            } else if (msum < 0) {
                h--;
                msum += 60;
            }
            ans += (h - H + 24)%24 * 60 + msum;
        }
        System.out.println(ans);
    }
}