#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
    double xa,ya,xb,yb,xc,yc,xd,yd;
    char a[10];
    while(scanf("%s",a)!=EOF)
    {
        if('A'<=a[0]&&a[0]<='Z') return 0;
        else
        sscanf(a,"%lf",&xa);
        scanf("%lf%lf%lf%lf%lf%lf%lf",&ya,&xb,&yb,&xc,&yc,&xd,&yd);
        double x1=xb-xa, y1=yb-ya, x2=xd-xc, y2=yd-yc;
        if(x1*x2+y1*y2==0)
            printf("YSE\n");
        else printf("NO\n");
    }
    return 0;
}