#include<bits/stdc++.h>
using namespace std;

#define int long long
typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define all(v) (v).begin(),(v).end()
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define fi first
#define se second
template<typename A,typename B>inline void chmin(A &a,B b){if(a>b)a=b;}
template<typename A,typename B>inline void chmax(A &a,B b){if(a<b)a=b;}

signed main(){
    pair<int,int>v[6];
    rep(i,6){
        cin>>v[i].fi>>v[i].se;
        if(v[i].fi>v[i].se)swap(v[i].fi,v[i].se);
    }

    sort(v,v+6);
    if(v[0]==v[1]&&v[2]==v[3]&&v[4]==v[5]&&v[0].fi==v[2].fi&&v[0].se==v[4].fi&&v[2].se==v[4].se)cout<<"yes"<<endl;
    else cout<<"no"<<endl;
    return 0;
}