#include <iostream>
#include <cstdio>
using namespace std;

int main(){
	while(1){
		double x[4], y[4];
		bool flag=false;
		
		for(int i=0; i<4; ++i){
			if(scanf(" %lf %lf", &x[i], &y[i]) == EOF){
				flag=true;
				break;
			}
		}
		if(flag) break;
		
		if(x[0]==x[1]){
			if(y[2]==y[3]) flag=true;
		}
		else if(x[2]==x[3]){
			if(y[0]==y[1]) flag=true;
		}
		else{
			double m=( (y[0]-y[1])/(x[0]-x[1]) ) * ( (y[2]-y[3])/(x[2]-x[3]) );
			if(m==-1) flag=true;
		}
		
		if(flag) printf("YES\n");
		else printf("NO\n");
	}

	return 0;
}