#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
    double xa,ya,xb,yb,xc,yc,xd,yd;
    while(scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&xa,&ya,&xb,&yb,&xc,&yc,&xd,&yd)!=EOF)
    {
        double x1=xb-xa, y1=yb-ya, x2=xd-xc, y2=yd-yc;
        if(abs(x1*x2+y1*y2)<1e-6)
            printf("YSE\n");
        else printf("NO\n");
    }
    return 0;
}