import java.util.Scanner;
public class Main{
    public static void main(String []args){
        Scanner sc = new Scanner(System.in);
        int num1 = sc.nextInt();
        int num2 = sc.nextInt();
        int num3 = sc.nextInt();
        int num4 = sc.nextInt();
        //统一将小时化为分钟
        int result=(num1*60+num2)-(num3*60+num4);
        System.out.println(Math.abs(result));

    }
}