#include<bits/stdc++.h>
using namespace std;
#define fst first
#define sec second
int main(){
  pair<int,int> x[6];
  for(int i=0;i<6;++i){
    cin>>x[i].fst>>x[i].sec;
    if(x[i].fst>x[i].sec) swap(x[i].fst,x[i].sec);
  }
  sort(x,x+6);
  pair<int,int> y[3];
  for(int i=0;i<6;i+=2){
    if(x[i]==x[i+1]) y[i/2]=x[i];
    else{ cout<<"no\n"; return 0; }
  }
  if(y[0].fst==y[1].fst && y[1].sec==y[2].sec && y[2].fst==y[0].sec) cout<<"yes\n";
  else cout<<"no\n";
  return 0;
}