1026 running time, C

#include <stdio.h>

int main()
{
    int a,b,h=0,m=0,s=0;

    scanf("%d %d",&a,&b);
    a = (b-a) /100;
    if( (a%100) >= 50 )   a++;

    h = a/3600;
    m = (a%3600)/60;
    s = (a%3600)%60;

    printf("%02d:%02d:%02d",h,m,s);


    return 0;    
}