zoj 2229 Ride to School

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
typedef struct
{
    int v;
    int settime;
    int time;
}person;
person p[10010];
int cmp(const void *a,const void *b)
{
    person *c=(person *)a;
    person *d=(person *)b;
    return c->time>d->time;
}
int main(void)
{
    
    int n,i;
    while(scanf("%d",&n)!=EOF&&n!=0)
    {
        for(i=0;i<n;i++)
        {
            scanf("%d%d",&p[i].v,&p[i].settime);
            p[i].time=ceil((double)p[i].settime+(4.5/p[i].v)*3600);/*ceil 0.1以上都进1*/
        }
        qsort(p,n,sizeof(person),cmp);
        for(i=0;i<n;i++)
        {
            if(p[i].settime>=0)
            {
                printf("%d\n",p[i].time);
                break;
            }
        }
    }
    return 0;
}