import java.util.Scanner;


public class Main {
	public static void main(String[] a) {
		Scanner s=new Scanner(System.in);
		s.next();
		s.useDelimiter("[ :\r\n]+");
		int Z=0;while(s.hasNext()){
			int H=s.nextInt(),M=s.nextInt(),h=s.nextInt(),m=s.nextInt(),S=H*60+M,E=h*60+m,T=S<E?E-S:1440-S+E;Z+=T;
		}
		System.out.println(Z);
	}
}