为什么在机器上能运行，提交后却不能AC呢

#include"stdio.h"
main()
{
int x1,x2,x3,x4;
int y1,y2,y3,y4;
int k1,k2,k3;
while(scanf("%d",&x1))
{
scanf("%d%d%d",&y1,&x2,&y2);
scanf("%d%d%d%d",&x3,&y3,&x4,&y4);
k1=(y2-y1)/(x2-x1);
k2=(y4-y3)/(x4-x3);
if(k1!=k2)
printf("Yes/n");
else
{
k3=(y4-y1)/(x4-x1);
if(k3==k1)
printf("Yes/n");
else
printf("No/n");
}
}

}

问题地址
http://acm.zjgsu.edu.cn/JudgeOnline/showproblem?problem_id=1398