17 计算火车运行时间

#include<stdio.h>
#include<math.h>
int main()
{
        int starttime;
        int arrivetime;
        int min,hour;
    scanf("%d %d", &starttime, &arrivetime);

    min = arrivetime%100 - starttime%100;
    hour = arrivetime/100 - starttime/100;
    hour = fabs(hour);

    if(min < 0)
    {
        min = min+60;
        hour = hour -1;
    }
printf("%02d:%02d",hour,min);
    return 0;
}