#include<iostream>
#include<algorithm>
#define X first
#define Y second
using namespace std;
pair<int,int> z[6];
int main(){
	int a,b,t;
	for(int i=0;i<6;i++){
		cin>>a>>b;
		if(a>b)t=a,a=b,b=t;
		z[i].X=a,z[i].Y=b;
	}
	sort(z,z+6);
	bool ok=true;
	if(z[0]!=z[1]||z[2]!=z[3]||z[4]!=z[5])ok=false;
	if(z[0].X!=z[2].X||z[0].Y!=z[4].X||z[2].Y!=z[4].Y)ok=false;
	if(ok)cout<<"yes"<<endl;
	else cout<<"no"<<endl;
	return 0;
}