#include <iostream>
#include <map>
#include <utility>
using namespace std;

int main(void){
	std::map<pair<int,int>,bool > m;
	int a,b;
	for(int i=0;i<6;i++){
		cin>>a>>b;
		if(s[make_pair(a,b)]){
			cout<<"no"<<endl;
			return 0;
		}
		s[make_pair(a,b)]=true;
	}
	if(m.size()==3)cout<<"yes"<<endl;
	else cout<<"no"<<endl;
	return 0;
}