分支-12. 计算火车运行时间

import java.util.Scanner;
import java.text.DecimalFormat;  
public class Main 
{
    public static void main(String[] args)
    {
        DecimalFormat df = new DecimalFormat("00");
        Scanner input = new Scanner(System.in);
        int start = input.nextInt();
        int end = input.nextInt(); 
        int hh1 =  (int)(start / 100);
        int hh2 =  (int)(end / 100);
        int mm1 = start - hh1 * 100;
        int mm2 = end - hh2 * 100;
        if(mm2 >= mm1)
            System.out.print(df.format(hh2 - hh1)+":"+df.format(mm2 - mm1));
        else
            System.out.print(df.format(hh2 - hh1 -1)+":"+df.format(mm2 + 60 - mm1));    
    }
}