#include <iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<math.h>
using namespace std;
typedef long long ll;
#define int long long
typedef vector<int> VI;
typedef pair<int, int> pii;
#define fore(i,a) for(auto &i:a)
#define REP(i,n) for(int i=0;i<n;i++)
#define eREP(i,n) for(int i=0;i<=n;i++)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define eFOR(i,a,b) for(int i=(a);i<=(b);++i)
#define SORT(c) sort((c).begin(),(c).end())
#define rSORT(c) sort((c).rbegin(),(c).rend())
#define LB(x,a) lower_bound((x).begin(),(x).end(),(a))
#define UB(x,a) upper_bound((x).begin(),(x).end(),(a))
#define INF 1000000000
#define LLINF 9223372036854775807
#define mod 1000000007
//vector<vector<int> > dp;
//vector<vector<vector<int> > > vvvi;
//dp=vector<vector<int> >(N, vector<int>(M,0));
//vector<pair<int,int> > v;
//v.push_back(make_pair(x,y));
//priority_queue<int,vector<int>, greater<int> > q2;



signed main(){
cin.tie(0);
ios::sync_with_stdio(false);

	vector<pii> A;
	int a, b, c, d, e, f;
	REP(i, 6) {
		int s, t;
		cin >> s >> t;
		A.push_back(pii(min(s, t), max(s, t)));
	}
	SORT(A);
	for (int i = 0; i < 6; i += 2) {
		if (A[i].first != A[i + 1].first || A[i].second != A[i + 1].second) {
			cout << "no" << endl;
			return 0;
		}
		else {
			if (i == 0) {
				a = A[i].first;
				b = A[i].second;
			}
			else if (i == 2) {
				c = A[i].first;
				d = A[i].second;
			}
			else {
				e = A[i].first;
				f = A[i].second;
			}
		}
	}
	bool ans = false;
	if (a == c) {
		if (b == f && d == e)ans = 1;
		else if (b == e && d == f)ans = 1;
	}
	else if (a == d) {
		if (b == f && c == e)ans = 1;
		else if (b == e && c == f)ans = 1;
	}
	else if (a == e) {
		if (b == c && d == f)ans = 1;
		else if (b == d && c == f)ans = 1;
	}
	else if (a == f) {
		if (b == c && d == e)ans = 1;
		else if (b == d && c == e)ans = 1;
	}
//	cout << a << " " << b << " " << c << " " << d << " " << e << " "<<f << endl;
	cout << (ans ? "yes" : "no") << endl;
	return 0;
}


