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

int main(){
  
  pair<int, int> a[6];

  for(int i=0;i<6;i++){
    cin>>a[i].first>>a[i].second;
    if(a[i].first>a[i].second) swap(a[i].first, a[i].second);
  }

  sort(a, a+6);

  pair<int, int> b[3];

  int cnt=0;
  for(int i=0;i<6;i+=2){
    if(a[i]==a[i+1]) b[cnt++]=a[i];
    else{
      cout<<"no"<<endl;
      return 0;
    }
  }

  if(b[0].first==b[1].first&&b[1].second==b[2].second&&b[2].first==b[0].second) cout<<"yes"<<endl;
  else cout<<"no"<<endl;
  
  return 0;
}