Problem:
Score : 200 points

Problem Statement

There are four towns, numbered 1,2,3 and 4.
Also, there are three roads. The i-th road connects different towns a_i and b_i bidirectionally.
No two roads connect the same pair of towns. Other than these roads, there is no way to travel between these towns, but any town can be reached from any other town using these roads.

Determine if we can visit all the towns by traversing each of the roads exactly once.

Constraints

1 \leq a_i,b_i \leq 4(1\leq i\leq 3)

a_i and b_i are different. (1\leq i\leq 3)

No two roads connect the same pair of towns.

Any town can be reached from any other town using the roads.

Input

Input is given from Standard Input in the following format:

a_1 b_1
a_2 b_2
a_3 b_3

Output

If we can visit all the towns by traversing each of the roads exactly once, print YES; otherwise, print NO.

Sample Input 1

4 2
1 3
2 3

Sample Output 1

YES

We can visit all the towns in the order 1,3,2,4.

Sample Input 2

3 2
2 4
1 2

Sample Output 2

NO

Sample Input 3

2 1
3 2
4 3

Sample Output 3

YES

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

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

template <class T> using V = vector<T>;
template <class T> using VV = V<V<T>>;
template <class T> using VVV = V<VV<T>>;
template <class S, class T> using P = pair<S, T>;
template <class... T> using TP = tuple<T...>;

using ll = long long;
using ull = unsigned long long;
using dbl = double;
using str = string;
using vll = V<ll>;
using vvll = V<vll>;
using vvvll = V<vvll>;
using pl = P<ll, ll>;
using tl = TP<ll, ll, ll>;
using vpl = V<pl>;
using vvpl = V<vpl>;
using vtl = V<tl>;
using vvtl = V<vtl>;
using vs = V<str>;
using vvs = V<vs>;
using vd = V<dbl>;
using vvd = V<vd>;
using qll = queue<ll>;
using qpl = queue<pl>;
using stll = stack<ll>;
using stpl = stack<pl>;
using mapll = map<ll, ll>;
using setll = set<ll>;
using pqll = priority_queue<ll>;

//#define int ll
#define fi first
#define se second
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define pob pop_back()
#define pf push_front
#define pof pop_front()
#define sz size()
#define bgn begin()
#define en end()
#define asn assign
#define emp empty()
#define fr front()
#define bk back()
#define clr clear()
#define ins insert
#define ers erase
#define res resize
#define tp top()
#define p_q priority_queue
#define inv inverse()

#define FOR(i,a,b) for(ll i=(a);i<=(ll)(b);i++)
#define rFOR(i,a,b) for(ll i=(b);i>=(ll)(a);i--)
#define REP(i,a) FOR((i),0,(ll)(a)-1)
#define REP0(i,a) FOR((i),0,(ll)(a))
#define REP1(i,a) FOR((i),1,(ll)(a))
#define rREP(i,a) rFOR((i),0,(ll)(a)-1)
#define rREP0(i,a) rFOR((i),0,(ll)(a))
#define rREP1(i,a) rFOR((i),1,(ll)(a))
#define ROR(v,i) for(auto &(i):(v))
#define IOTA(a,n) iota((a).bgn,(a).en,(n))
#define SORT(a) sort((a).bgn,(a).en)
#define rSORT(a) sort((a).rbegin(),(a).rend())
#define UNIQUE(a) (a).erase(unique((a).bgn,(a).en),(a).en)
#define PREVP(a) prev_permutation((a).bgn,(a).en)
#define NEXTP(a) next_permutation((a).bgn,(a).en)
#define BINS(a,b) binary_search((a).bgn,(a).en,(b))
#define LOWB(a,b) (lower_bound((a).bgn,(a).en,(b))-(a).bgn)
#define UPB(a,b) (upper_bound((a).bgn,(a).en,(b))-(a).bgn)
#define CNT(a,b) count((a).bgn,(a).en,b)
#define SUM(a) accumulate((a).bgn,(a).en,0)
#define REV(a) reverse((a).bgn,(a).en)
#define REGS(a,b) regex_search((a),regex(b))
#define REGM(a,b) regex_match((a),regex(b))
#define yn(a) cout <<((a)?"yes":"no")<<"\n";
#define Yn(a) cout <<((a)?"Yes":"No")<<"\n";
#define YN(a) cout <<((a)?"YES":"NO")<<"\n";
#define imp(a) cout <<((a)?"possible":"impossible")<<"\n";
#define Imp(a) cout <<((a)?"Possible":"Impossible")<<"\n";
#define IMP(a) cout <<((a)?"POSSIBLE":"IMPOSSIBLE")<<"\n";
#define fs(a) cout <<((a)?"second":"first")<<"\n";
#define Fs(a) cout <<((a)?"Second":"First")<<"\n";
#define FS(a) cout <<((a)?"SECOND":"FIRST")<<"\n";
//#define say(a) cout <<(a);
//#define sal(a) cout <<(a)<<"\n";
#define sak cout <<"\n";
#define sas cout <<" ";
#define sat cout <<"\t";
#define dbg(a) cerr <<(#a)<<": "<<(a)<<"\n";
#define dbgs(...) dal(#__VA_ARGS__);dal(__VA_ARGS__);
#define c2l(a) ((ll)(a-48))
#define a2l(a) ((ll)(a-97))
#define A2l(a) ((ll)(a-65))
#define l2c(a) ((char)(a+48))
#define l2a(a) ((char)(a+97))
#define l2A(a) ((char)(a+65))
#define DigN2(a) ((llabs(a)==0)?(1):((ll)(log2(double(llabs(a))))+1))
#define DigN10(a) ((llabs(a)==0)?(1):((ll)(log10(double(llabs(a))))+1))
#define Dig2(a,b) (((a)>>(b))&1)
#define Dig10(a,b) (ll)(((a)/((ll)(pow(10.0,(double)(b)))))%10)
#define Pow2(a) ((ll)(1)<<(a))
#define Pow10(a) ((ll)(pow(10.0,double(a))))
#define LSB(a) ((a)&(-(a)))
/*#define llin(a) ll (a);cin >>(a);
#define llin2(a,b) ll (a),(b);cin >>(a)>>(b);
#define llin3(a,b,c) ll (a),(b),(c);cin >>(a)>>(b)>>(c);
#define stin(a) string (a);cin >>(a);*/
#define vin(v) ROR((v),(i)){cin >>(i);};
#define vllin(N,v) vll (v)((N));vin(v);
#define vllin2(N,a,b) vll (a)(N),(b)(N);REP(i,N){cin>>(a)[i]>>(b)[i];};
#define vsin(N,v) vs (v)((N));vin(v);
#define rdn(a,b) ((a)/(b))
#define rou(a,b) ((((double(a)/double(b))-((a)/(b)))<0.5)?((a)/(b)):(((a)/(b))+1))
#define rup(a,b) ((((a)%(b))==0)?((a)/(b)):(((a)/(b))+1))
#define powll(a,b) (ll)(pow((double)(a),(double)(b)))
#define Triangle(x1,y1,x2,y2,x3,y3) (((x1)-(x2))*((y1)-(y3))-((x1)-(x3))*((y1)-(y2)))
#define tg(t,i) get<i>(t)

#define Id(x) get<0>(x)
#define Act(x) get<1>(x)
#define InvAct(x) get<2>(x)
#define mg(i,a) mt(i,a,lam(l))
//#define MonoidSet(T) TP<T, function<T(T, T)>>
#define GroupSet(T) TP<T, function<T(T, T)>, function<T(T, T)>>
#define CompareSet(T) TP<T, function<bool(T, T)>>
#define lam(lr) ([](auto l, auto r){return (lr);})
#define elam(lr) ([=](auto l, auto r){return (lr);})
#define clam(lr) ([&](auto l, auto r){return (lr);})
#define lamr(lr) ([](auto l, auto r){lr})
#define elamr(lr) ([=](auto l, auto r){lr})
#define clamr(lr) ([&](auto l, auto r){lr})
#define min(...) Operation(MIN,__VA_ARGS__)
#define max(...) Operation(MAX,__VA_ARGS__)
#define gcd(...) Operation(GCD,__VA_ARGS__)
#define lcm(...) Operation(LCM,__VA_ARGS__)
#define vmin(...) VOperation(MIN,__VA_ARGS__)
#define vmax(...) VOperation(MAX,__VA_ARGS__)
#define vgcd(...) VOperation(GCD,__VA_ARGS__)
#define vlcm(...) VOperation(LCM,__VA_ARGS__)
#define vsum(...) VOperation(ADD,__VA_ARGS__)
#define vpro(...) VOperation(MUL,__VA_ARGS__)
#define emin(a, ...) ((a)=min((a),__VA_ARGS__))
#define emax(a, ...) ((a)=max((a),__VA_ARGS__))
#define egcd(a, ...) ((a)=gcd((a),__VA_ARGS__))
#define elcm(a, ...) ((a)=lcm((a),__VA_ARGS__))
#define ope Operation
#define vope VOperation

#define svll SumV<ll>
#define svvll SumV2<ll>

#define li(...) ll __VA_ARGS__;Input(__VA_ARGS__);
#define si(...) str __VA_ARGS__;Input(__VA_ARGS__);
//#define vli(size, ...) vll __VA_ARGS__;vInitInput(size,__VA_ARGS__);
#define vlr(size, ...) vll __VA_ARGS__;vInitInputR(size,__VA_ARGS__);
#define vlc(size, ...) vll __VA_ARGS__;vInitInputC(size,__VA_ARGS__);
#define vli(size, ...) vll __VA_ARGS__;vInitInputR(size,__VA_ARGS__);
#define vsr(size, ...) vs __VA_ARGS__;vInitInputR(size,__VA_ARGS__);
#define vsc(size, ...) vs __VA_ARGS__;vInitInputC(size,__VA_ARGS__);
#define vsi(size, ...) vs __VA_ARGS__;vInitInputR(size,__VA_ARGS__);
#define vli2(rowSize,columnSize, ...) vvll __VA_ARGS__;vInitInput2(rowSize,columnSize,__VA_ARGS__);
#define vplr(size, ...) vpl __VA_ARGS__;vInitInputR(size,__VA_ARGS__);
#define vplc(size, ...) vpl __VA_ARGS__;vInitInputC(size,__VA_ARGS__);
#define vpli(size, ...) vpl __VA_ARGS__;vInitInputR(size,__VA_ARGS__);

const ll MOD = 1e9 + 7;
//const ll MOD = 998244353;
//const ll MOD = 924844033;
//const ll MOD = 9007199254740881;
const ll INF = 1LL << 60;//1.15e18
const double PI = acos(-1.0);
const vll DX = { 0,-1,0,1,0,-1,1,1,-1 };
const vll DY = { 0,0,-1,0,1,-1,-1,1,1 };
const str alp = "abcdefghijklmnopqrstuvwxyz";
const str ALP = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

template <class T> auto GetVectorValueType(T v) { return v; }
template <class T> auto GetVectorValueType(V<T> v) { return GetVectorValueType(T()); }

template <class S, class T> istream &operator>>(istream &in, P<S, T> &p) { return in >> p.fi >> p.se; }
template <class T> istream &operator>>(istream &in, V<T> &v) { REP(i, v.sz) in >> v[i]; return in; }

void Input() {}
template <class Var, class... Args> void Input(Var& var, Args&... args) {
	cin >> var;
	Input(args...);
}

void vInit(ll size) {}
template <class T, class... Args> void vInit(ll size, V<T>& v, Args&... args) {
	v.res(size);
	vInit(size, args...);
}
void vInput(ll size) {}
template <class T, class... Args> void vInput(ll size, V<T>& v, Args&... args) {
	REP(i, size) cin >> v[i];
	vInput(size, args...);
}
void vInputR(ll size) {}
template <class T, class... Args> void vInputR(ll size, V<T>& v, Args&... args) {
	REP(i, size) cin >> v[i];
	vInputR(size, args...);
}
void vInputNumC(ll num) {}
template <class T, class... Args> void vInputNumC(ll num, V<T>& v, Args&... args) {
	cin >> v[num];
	vInputNumC(num, args...);
}
void vInputC(ll size) {}
template <class... Args> void vInputC(ll size, Args&... args) {
	REP(i, size) vInputNumC(i, args...);
}
void vInitInputR(ll size) {}
template <class... Args> void vInitInputR(ll size, Args&... args) {
	vInit(size, args...);
	vInputR(size, args...);
}
void vInitInputC(ll size) {}
template <class... Args> void vInitInputC(ll size, Args&... args) {
	vInit(size, args...);
	vInputC(size, args...);
}
void vInit2(ll rowSize, ll columnSize) {}
template <class T, class... Args> void vInit2(ll rowSize, ll columnSize, VV<T>& v, Args&... args) {
	v.asn(rowSize, V<T>(columnSize));
	vInit2(rowSize, columnSize, args...);
}
void vInput2(ll rowSize, ll columnSize) {}
template <class T, class... Args> void vInput2(ll rowSize, ll columnSize, VV<T>& v, Args&... args) {
	REP(r, rowSize) {
		REP(c, columnSize) {
			cin >> v[r][c];
		}
	}
	vInput2(rowSize, columnSize, args...);
}
void vInitInput2(ll rowSize, ll columnSize) {}
template <class... Args> void vInitInput2(ll rowSize, ll columnSize, Args&... args) {
	vInit2(rowSize, columnSize, args...);
	vInput2(rowSize, columnSize, args...);
}

template <class S, class T> ostream &operator<<(ostream &out, const P<S, T> &p) {
	return out << "[" << p.fi << ", " << p.se << "]";
}
template <class T> ostream &operator<<(ostream &out, V<T> &v) {
	if (v.emp) return out << "{}";
	else {
		auto itr = v.bgn;
		out << "{" << *itr;
		itr++;
		while (itr != v.en) {
			out << ", " << *itr;
			itr++;
		}
		out << "}";
		return out;
	}
}
template <class S, class T> ostream &operator<<(ostream &out, const map<S, T> &m) {
	if (m.emp) return out << "<[]>";
	else {
		auto itr = m.bgn;
		out << "< [" << (itr->fi) << ": " << (itr->se);
		itr++;
		while (itr != m.en) {
			out << "], [" << (itr->fi) << ": " << (itr->se);
			itr++;
		}
		out << "] >";
		return out;
	}
}
template <class T> ostream &operator<<(ostream &out, const set<T> &s) {
	if (s.emp) return out << "<>";
	else {
		auto itr = s.bgn;
		out << "<" << *itr;
		itr++;
		while (itr != s.en) {
			out << ", " << *itr;
			itr++;
		}
		out << ">";
		return out;
	}
}

void say() {}
template <class T> void say(T t) { cout << t; }
template <class Head, class... Body> void say(Head head, Body... body) {
	cout << head << " ";
	say(body...);
}
void sal() { cout << "\n"; }
template <class... Args> void sal(Args... args) {
	say(args...);
	cout << "\n";
}

void day() {}
template <class T> void day(T t) { cerr << t; }
template <class Head, class... Body> void day(Head head, Body... body) {
	cerr << head << " ";
	day(body...);
}
void dal() { cerr << "\n"; }
template <class... Args> void dal(Args... args) {
	day(args...);
	cerr << "\n";
}

void salv() {}
template <class T> void salv(V<T> v) {
	if (v.emp) sal();
	else {
		auto itr = v.bgn;
		say(*itr);
		itr++;
		while (itr != v.en) {
			sas;
			say(*itr);
			itr++;
		}
		sak;
	}
}
template <class T> void salv(VV<T> v) {
	if (v.emp) sal();
	else {
		ROR(v, i) salv(i);
	}
}
template <class T, class... Args> void salv(T v, Args... args) {
	salv(v);
	salv(args...);
}


template <class L, class R> auto Gcd(L l, R r) -> decltype(l + r) {
	if (l < r) swap(l, r);
	return r ? Gcd(r, l%r) : l;
}
template <class L, class R> auto Lcm(L l, R r) {
	if (!l || !r) return 0;
	return l / Gcd(l, r) * r;
}

/*
auto LES = mp(INF, lam(return l < r;));
auto GRT = mp(-INF, lam(return l > r;));
auto EQ = mp(0, lam(return l == r;));

auto ADD = mp(0, lam(return l + r;));
auto SUB = mp(0, lam(return l - r;));
auto MUL = mp(1, lam(return l * r;));
auto DIV = mp(1, lam(return l / r;));
auto MDL = mp(1, lam(return l % r;));
auto XOR = mp(0, lam(return l ^ r;));
auto OR = mp(0, lam(return l | r;));
auto AND = mp(((ll)(1) << 63) - 1, lam(return l & r;));
auto MIN = mp(INF, lam(return (l < r) ? l : r;));
auto MAX = mp(-INF, lam(return (l > r) ? l : r;));
auto GCD = mp(0, lam(return Gcd(l, r);));
auto LCM = mp(1, lam(return Lcm(l, r);));
*/

auto LES = mp(INF, lam(l < r));
auto GRT = mp(-INF, lam(l > r));
auto EQ = mp(0, lam(l == r));

auto ADD = mt(0, lam(l + r), lam(l - r));
auto MUL = mt(1, lam(l * r), lam(l / r));
auto XOR = mt(0, lam(l ^ r), lam(l ^ r));
auto OR = mg(0, lam(l | r));
auto AND = mg(((ll)(1) << 63) - 1, lam(l & r));
auto MIN = mg(0, lam((l < r) ? l : r));
auto MAX = mg(0, lam((l > r) ? l : r));
auto GCD = mg(0, lam(Gcd(l, r)));
auto LCM = mg(0, lam(Lcm(l, r)));

template <class OperationType> auto Operation(OperationType A) { return Id(A); }
template <class OperationType, class T> auto Operation(OperationType A, T x) { return x; }
template <class OperationType, class T, class... Args> auto Operation(OperationType A, T x, Args... args) {
	auto tmp = Operation(A, args...);
	return Act(A)(x, tmp);
}

template <class OperationType> auto VOperation(OperationType A) { return Id(A); }
template <class OperationType, class T> auto VOperation(OperationType A, T x) { return x; }
template <class OperationType, class T> auto VOperation(OperationType A, V<T> v) {
	if (v.emp) {
		decltype(GetVectorValueType(T())) tmp = Id(A);
		return tmp;
	}
	auto tmp = VOperation(A, v[0]);
	FOR(i, 1, v.sz - 1) tmp = Act(A)(tmp, VOperation(A, v[i]));
	return tmp;
}
template <class OperationType, class T, class... Args> auto VOperation(OperationType A, T x, Args... args) {
	auto xResult = VOperation(A, x);
	auto tmp = VOperation(A, args...);
	return Act(A)(xResult, tmp);
}


ll Bset(ll a, ll b, ll c) {
	if (c) a |= b;
	else a &= ~b;
	return a;
}


struct UFT {

public:
	ll tsize;
	ll mode;
	vll par;
	vll rank;
	UFT(ll tsizeget, ll modeget = 0){
		tsize = tsizeget;
		mode = modeget;
		par.asn(tsize, -1);
		if (!mode) rank.res(tsize, 0);
	}
	ll root(ll x) {
		return par[x] < 0 ? x : par[x] = root(par[x]);
	}
	bool isRoot(ll x) {
		return x == root(x);
	}
	bool same(ll x, ll y) {
		return root(x) == root(y);
	}
	void merge(ll x, ll y) {
		x = root(x);
		y = root(y);
		if (x == y) return;
		if (mode) {
			par[x] += par[y];
			par[y] = x;
		}
		else {
			if (rank[x] < rank[y]) {
				par[y] += par[x];
				par[x] = y;
			}
			else {
				par[x] += par[y];
				par[y] = x;
				if (rank[x] == rank[y]) rank[x]++;
			}
		}
	}
	ll size(ll x) {
		return -par[root(x)];
	}
};

template <class T> struct pUFT {

public:

	ll tsize;
	ll now;
	vll par;
	vll rank;
	vll mtime;
	vvll sizepi;
	VV<T> sizepv;
	V<T> elm;
	GroupSet(T) Add;

	pUFT(ll tsize, GroupSet(T) Add = ADD) : tsize(tsize), Add(Add) { init(); }
	void init() {
		now = 0;
		par.asn(tsize, -1);
		rank.asn(tsize, 0);
		mtime.asn(tsize, INF);
		sizepi.asn(tsize, { 0 });
		sizepv.asn(tsize, {});
	}
	void set(ll x, T s) {
		elm[x] = s;
		sizepv[x] = { s };
	}
	ll root(ll x, ll t) {
		return (mtime[x] > t) ? x : root(par[x], t);
	}
	bool same(ll x, ll y, ll t) {
		return root(x, t) == root(y, t);
	}
	ll merge(ll x, ll y) {
		now++;
		x = root(x, now);
		y = root(y, now);
		if (x != y) {
			if (rank[x] < rank[y]) {
				elm[y] = Act(Add)(elm[x], elm[y]);
				sizepi[y].pb(now);
				sizepv[y].pb(elm[y]);
				par[x] = y;
				mtime[x] = now;
			}
			else {
				elm[x] = Act(Add)(elm[x], elm[y]);
				sizepi[x].pb(now);
				sizepv[x].pb(elm[x]);
				par[y] = x;
				mtime[y] = now;
				if (rank[x] == rank[y]) rank[x]++;
			}
		}
		return now;
	}
	T size(ll x, ll t) {
		x = root(x, t);
		return sizepv[x][UPB(sizepi[x], t) - 1];
	}

};

struct wUFT {
public:
	ll tsize;
	ll mode;
	vll par;
	vll rank;
	vll dweight;
	wUFT(ll tsizeget, ll modeget = 0) {
		tsize = tsizeget;
		mode = modeget;
		par.asn(tsize, -1);
		if (!mode) rank.res(tsize, 0);
		dweight.asn(tsize, 0);
	}
	ll root(ll x) {
		if (par[x] < 0) return x;
		else {
			ll r = root(par[x]);
			dweight[x] += dweight[par[x]];
			return par[x] = r;
		}
	}
	ll weight(ll x) {
		root(x);
		return dweight[x];
	}
	ll diff(ll x, ll y) {
		return weight(y) - weight(x);
	}
	bool isRoot(ll x) {
		return x == root(x);
	}
	bool same(ll x, ll y) {
		return root(x) == root(y);
	}
	void merge(ll x, ll y, ll w) {
		w += weight(x);
		w -= weight(y);
		x = root(x);
		y = root(y);
		if (x == y) return;
		if (mode) {
			par[x] += par[y];
			par[y] = x;
		}
		else {
			if (rank[x] < rank[y]) {
				par[y] += par[x];
				par[x] = y;
				dweight[x] = -w;
			}
			else {
				par[x] += par[y];
				par[y] = x;
				if (rank[x] == rank[y]) rank[x]++;
				dweight[y] = w;
			}
		}
	}
	ll size(ll x) {
		return -par[root(x)];
	}
};

template <class T> struct sUFT {

public:
	ll tsize;
	ll mode;
	vll par;
	vll rank;
	GroupSet(T) Add;
	V<T> elm;
	sUFT(ll tsize, GroupSet(T) Add = ADD, ll mode = 0) : tsize(tsize), Add(Add), mode(mode) { init(); }
	void init() {
		par.asn(tsize, -1);
		if (!mode) rank.res(tsize, 0);
		elm.asn(tsize, Id(Add));
	}
	ll root(ll x) {
		return par[x] < 0 ? x : par[x] = root(par[x]);
	}
	bool isRoot(ll x) {
		return x == root(x);
	}
	bool same(ll x, ll y) {
		return root(x) == root(y);
	}
	void merge(ll x, ll y) {
		x = root(x);
		y = root(y);
		if (x == y) return;
		if (mode) {
			elm[x] = Act(Add)(elm[x], elm[y]);
			par[y] = x;
		}
		else {
			if (rank[x] < rank[y]) {
				elm[y] = Act(Add)(elm[x], elm[y]);
				par[x] = y;
			}
			else {
				elm[x] = Act(Add)(elm[x], elm[y]);
				par[y] = x;
				if (rank[x] == rank[y]) rank[x]++;
			}
		}
	}
	T size(ll x) {
		return elm[root(x)];
	}
	T& operator[](ll x) { return elm[x]; }
};

template <typename valtype> class SegT {

public:

	ll size;
	vector<valtype> v;

	valtype initv;
	function<valtype(valtype x, valtype y)> calc;

	SegT() {}
	SegT(const SegT &segt) {}

	SegT(ll sizeget, ll modeget = 0) {
		sizeset(sizeget);
		modeset(modeget);
		init();
	}
	SegT(vector<valtype> cpyvec, ll modeget = 0) {
		sizeset(cpyvec.sz);
		modeset(modeget);
		init();
		copy(cpyvec);
	}
	SegT(ll sizeget, valtype initvget, function<valtype(valtype x, valtype y)> calcget) {
		sizeset(sizeget);
		initv = initvget;
		calc = calcget;
		init();
	}
	SegT(vector<valtype> cpyvec, valtype initvget, function<valtype(valtype x, valtype y)> calcget) {
		sizeset(cpyvec.sz);
		initv = initvget;
		calc = calcget;
		init();
		copy(cpyvec);
	}
	void sizeset(ll rsize) {
		size = DigN2(rsize);
		if (rsize == Pow2(size - 1)) size--;
		return;
	}
	void modeset(ll mode) {
		switch (mode) {
		case 0:
			initv = 0;
			calc = [](valtype x, valtype y) {return x + y; };
			break;
		case 1:
			initv = INF;
			calc = [](valtype x, valtype y) {return min(x, y); };
			break;
		case 2:
			initv = -INF;
			calc = [](valtype x, valtype y) {return max(x, y); };
			break;
		}
		return;
	}
	void init() {
		v.asn(Pow2(size + 1) - 1, initv);
	}
	void copy(vector<valtype> cpyvec) {
		REP(i, min(cpyvec.sz, Pow2(size))) set(i, cpyvec[i]);
	}
	ll i2v(ll i) const{
		if (i < 0 || i >= Pow2(size)) return -1;
		return Pow2(size) + i - 1;
	}
	ll top(ll i) const{
		if (i == 0) return -1;
		return (i - 1) / 2;
	}
	pl bot(ll i) const{
		if (i + 1 >= Pow2(size)) return mp(-1, -1);
		return mp(2 * i + 1, 2 * i + 2);
	}
	void set(ll i, valtype x) {
		i = i2v(i);
		v[i] = x;
		while (i > 0) {
			i = top(i);
			v[i] = calc(v[bot(i).fi], v[bot(i).se]);
		}
		return;
	}
	void add(ll i, valtype x) {
		set(i, v[i2v(i)] + x);
		return;
	}
	valtype operator[](const ll &i) const {
		return v[i2v(i)];
	}
//	valtype que(ll a = 0, ll b = Pow2(size) - 1) {
	valtype que(ll a, ll b) {
		if (a == b) return v[i2v(a)];
		if (a > b) return initv;//swap(a, b);
		valtype ans = initv;
		ll ai = i2v(a);
		ll bi = i2v(b);
		FOR(i, 1, size + 1) {
			if (a > b) break;
			if (a%Pow2(i)) {
				ans = calc(ans, v[ai]);
				a += Pow2(i - 1);
				ai = top(ai) + 1;
			}
			else {
				ai = top(ai);
			}
			if (a > b) break;
			if ((b + 1) % Pow2(i)) {
				ans = calc(ans, v[bi]);
				b -= Pow2(i - 1);
				bi = top(bi) - 1;
			}
			else {
				bi = top(bi);
			}
			if (a > b) break;
		}
		return ans;
	}
	valtype que(ll b) {
		return que(0, b);
	}
	valtype que() {
		return que(0, Pow2(size) - 1);
	}


};


/*template <class Type> class DP {

public:

	vector<Type> v;
	Type initv;
	vll size, block;

	DP() {}
	DP(const DP &dp) {}

	template<class... Args> DP(Args... args) {
		block.asn(1, 1);
		Initialize(args...);
	}

	void Initialize(Type initv_) {
		initv = initv_;
		v.asn(block.bk, initv);
	}
	template<class... Args> void Initialize(ll val, Args... args) {
		size.pb(val);
		block.pb(block.bk*val);
		Initialize(args...);
	}



};*/


pl Bezout(ll a, ll b) {
	if (b != 0) {
		pl xy;
		xy = Bezout(b, a%b);
		return mp(xy.se, xy.fi - ((a / b)*xy.se));
	}
	else {
		return mp(1, 0);
	}
}
pl Bez(ll a, ll b, ll c) {
	pl xy;
	ll x, y, z, gc;
	xy = Bezout(a, b);
	gc = gcd(a, b);
	if (c%gc != 0) return mp(-1, -1);
	x = xy.fi*(c / gc); y = xy.se*(c / gc);
	if (x < 0) z = rup(-x, (b / gc));
	if (x >= 0) z = -x / (b / gc);
	x += z * (b / gc);
	y -= z * (a / gc);
	return mp(x, y);
}

ll DigS10(ll n) {
	ll ans = 0;
	while(1) {
		ans += n % 10;
		n /= 10;
		if (!n) break;
	}
	return ans;
}

ll isP(ll n) {
	if (n <= 1) return 0;
	FOR(i, 2, (ll)sqrt(n) + 1) {
		if (n%i == 0) return 0;
	}
	return 1;
}

ll Tot(ll n) {
	if (n <= 0) return 0;
	ll ans = n, x = 2;
	while (x*x <= n) {
		if (n%x == 0) {
			ans -= ans / x;
			while (n%x == 0) n /= x;
		}
		x++;
	}
	if (n > 1) ans -= ans / n;
	return ans;
}

template <class T> struct Graph {
public:
	ll vSize;
	ll eMode;
	ll mapMode;
	GroupSet(T) Add;
	CompareSet(T) Less;
	CompareSet(T) Equal;
	VV<P<T, ll>> adj;
	map<pl, T> len;
	Graph(ll vSize, ll eMode = 0, ll mapMode = 0, GroupSet(T) Add = ADD, CompareSet(T) Less = LES, CompareSet(T) Equal = EQ) : vSize(vSize), eMode(eMode), mapMode(mapMode), Add(Add), Less(Less), Equal(Equal) {}
	void Init() {
		adj.asn(vSize, V<P<T, ll>>());
	}
	void AddE(ll x, ll y, T cost) {
		iAddE(x, y, cost);
		if (!eMode) iAddE(y, x, cost);
	}
	void iAddE(ll x, ll y, T cost) {
		adj[x].pb(mp(cost, y));
		if (mapMode) len[mp(x, y)] = cost;
	}
	P<bool, T> getE(ll x, ll y) {
		if (!len.count(mp(x, y))) return mp(false, Id(Less));
		return mp(true, len[mp(x, y)]);
	}
	V<T> Dijk(ll x) {
		V<T> ans(vSize, Id(Less));
		if (x < 0 || x >= vSize) return ans;
		SegT<P<T, ll>> segt(vSize, mp(Id(Less), -1), clamr(
			if (l.se < 0) return r;
		if (r.se < 0) return l;
		return Act(Less)(l.fi, r.fi) ? l : r;
		));
		segt.set(x, mp(Id(Add), x));
		P<T, ll> now;
		while ((now = segt.que(0, vSize - 1)).se >= 0) {
			ans[now.se] = segt[now.se].fi;
			segt.set(now.se, mp(Id(Less), -2));
			ROR(adj[now.se], i) {
				if (segt[i.se].se == -2) continue;
				if (segt[i.se].se == -1) {
					segt.set(i.se, mp(Act(Add)(ans[now.se], i.fi), i.se));
					continue;
				}
				if (Act(Less)(Act(Add)(ans[now.se], i.fi), segt[i.se].fi)) {
					segt.set(i.se, mp(Act(Add)(ans[now.se], i.fi), i.se));
					continue;
				}
			}
		}
		return ans;
	}
	V<P<T, vll>> rDijk(ll x) {
		V<P<T, vll>> ans(vSize, mp(Id(Less), vll()));
		if (x < 0 || x >= vSize) return ans;
		SegT<P<T, ll>> segt(vSize, mp(Id(Less), -1), clamr(
			if (l.se < 0) return r;
		if (r.se < 0) return l;
		return Act(Less)(l.fi, r.fi) ? l : r;
		));
		segt.set(x, mp(Id(Add), x));
		P<T, ll> now;
		while ((now = segt.que(0, vSize - 1)).se >= 0) {
			ans[now.se].fi = segt[now.se].fi;
			segt.set(now.se, mp(Id(Less), -2));
			ROR(adj[now.se], i) {
				if (segt[i.se].se == -2) continue;
				if (segt[i.se].se == -1) {
					segt.set(i.se, mp(Act(Add)(ans[now.se].fi, i.fi), i.se));
					ans[i.se].se = { now.se };
					continue;
				}
				if (Act(Less)(Act(Add)(ans[now.se].fi, i.fi), segt[i.se].fi)) {
					segt.set(i.se, mp(Act(Add)(ans[now.se].fi, i.fi), i.se));
					ans[i.se].se = { now.se };
					continue;
				}
				if (Act(Equal)(Act(Add)(ans[now.se].fi, i.fi), segt[i.se].fi)) {
					ans[i.se].se.pb(now.se);
					continue;
				}
			}
		}
		return ans;
	}

	T Prim(ll x = 0) {
		T ans = Id(Add);
		if (x < 0 || x >= vSize) return ans;
		SegT<P<T, ll>> segt(vSize, mp(Id(Less), -1), clamr(
			if (l.se < 0) return r;
		if (r.se < 0) return l;
		return Act(Less)(l.fi, r.fi) ? l : r;
		));
		segt.set(x, mp(Id(Add), x));
		P<T, ll> now;
		while ((now = segt.que(0, vSize - 1)).se >= 0) {
			ans = Act(Add)(ans, segt[now.se].fi);
			segt.set(now.se, mp(Id(Less), -2));
			ROR(adj[now.se], i) {
				if (segt[i.se].se == -2) continue;
				if (segt[i.se].se == -1) {
					segt.set(i.se, i);
					continue;
				}
				if (Act(Less)(i.fi, segt[i.se].fi)) {
					segt.set(i.se, i);
					continue;
				}
			}
		}
		return ans;
	}

	P<T, V<P<T, vll>>> rPrim(ll x = 0) {
		P<T, V<P<T, vll>>> ans = mp(Id(Add), V<P<T, vll>>(vSize, mp(Id(Less), vll())));
		if (x < 0 || x >= vSize) return ans;
		SegT<P<T, ll>> segt(vSize, mp(Id(Less), -1), clamr(
			if (l.se < 0) return r;
		if (r.se < 0) return l;
		return Act(Less)(l.fi, r.fi) ? l : r;
		));
		segt.set(x, mp(Id(Add), x));
		P<T, ll> now;
		while ((now = segt.que(0, vSize - 1)).se >= 0) {
			ans.se[now.se].fi = segt[now.se].fi;
			ans.fi = Act(Add)(ans.fi, ans.se[now.se].fi);
			segt.set(now.se, mp(Id(Less), -2));
			ROR(adj[now.se], i) {
				if (segt[i.se].se == -2) continue;
				if (segt[i.se].se == -1) {
					segt.set(i.se, i);
					ans.se[i.se].se = { now.se };
					continue;
				}
				if (Act(Less)(i.fi, segt[i.se].fi)) {
					segt.set(i.se, i);
					ans.se[i.se].se = { now.se };
					continue;
				}
				if (Act(Equal)(i.fi, segt[i.se].fi)) {
					ans.se[i.se].se.pb(now.se);
					continue;
				}
			}
		}
		return ans;
	}

};

template <class T> struct Sum {
public:
	V<T> v, s;
	ll size;
	GroupSet(T) Add;
	Sum(V<T> v, GroupSet(T) Add = ADD) : v(v), size(v.sz), Add(Add) { Init(); Calc(); }
	void Init() {
		s.asn(size + 1, Id(Add));
	}
	void Calc() {
		REP(i, size) s[i + 1] = Act(Add)(s[i], v[i]);
	}
	T operator()(ll x) {
		if (x < -1) x = -1;
		if (x > size - 1) x = size - 1;
		return s[x + 1];
	}
	T operator()(ll l, ll r) {
		if (l < 0) l = 0;
		if (r >= size) r = size - 1;
		if (l > r) return Id(Add);
		return InvAct(Add)(s[r + 1], s[l]);
	}
};
using sumll = Sum<ll>;

template <class T> struct Sum2 {
public:
	VV<T> v, s;
	ll RowSize, ColumnSize;
	GroupSet(T) Add;
	Sum2(VV<T> v, GroupSet(T) Add = ADD) : v(v), RowSize(v.sz), ColumnSize(v.sz ? v[0].sz : 0), Add(Add) { Init(); Calc(); }
	void Init() {
		s.asn(RowSize + 1, V<T>(ColumnSize + 1, Id(Add)));
	}
	void Calc() {
		REP1(r, RowSize) {
			REP1(c, ColumnSize) {
//				s[r][c] = InvAct(Add)(Act(Add)(Act(Add)(v[r - 1][c - 1], operator()(r - 1, c - 2)), operator()(r - 2, c - 1)), operator()(r - 2, c - 2));
				s[r][c] = Act(Add)(s[r][c - 1], v[r - 1][c - 1]);
			}
		}
		REP1(r, RowSize) {
			REP1(c, ColumnSize) {
				s[r][c] = Act(Add)(s[r - 1][c], s[r][c]);
			}
		}
	}
	T operator()(ll r, ll c) {
		if (r < -1) r = -1;
		if (c < -1) c = -1;
		if (r > RowSize - 1) r = RowSize - 1;
		if (c > ColumnSize - 1) c = ColumnSize - 1;
		return s[r + 1][c + 1];
	}
	T operator()(ll r1, ll c1, ll r2, ll c2) {
		if (r1 < 0) r1 = 0;
		if (c1 < 0) c1 = 0;
		if (r2 >= RowSize) r2 = RowSize - 1;
		if (c2 >= ColumnSize) c2 = ColumnSize - 1;
		if (r1 > r2) return Id(Add);
		if (c1 > c2) return Id(Add);
		return InvAct(Add)(Act(Add)(s[r2 + 1][c2 + 1], s[r1][c1]), Act(Add)(s[r2 + 1][c1], s[r1][c2 + 1]));
	}
};
using sumll2 = Sum2<ll>;

template <class T> struct Point2 {
public:
	VV<T> v;
	ll h, w;
	Point2() : h(0), w(0) {}
	Point2(ll h, ll w) : h(h), w(w) { asn(h, w); }
	Point2(ll h, ll w, T val) : h(h), w(w) { asn(h, w, val); }
	Point2(VV<T> cv) : h(cv.sz), w(cv.sz ? cv[0].sz : 0) { asn(h, w); copy(cv); }
	void assign(ll h, ll w) { v.asn(h, V<T>(w)); }
	void assign(ll h, ll w, ll val) { v.asn(h, V<T>(w, val)); }
	void copy(VV<T> cv) { REP(_h, h) REP(_w, w) v[_h][_w] = cv[_h][_w]; }
	T& operator()(ll h, ll w) { return v[h][w]; }
	T& operator()(pl p) { return v[p.fi][p.se]; }
	T& operator[](pl p) { return v[p.fi][p.se]; }
};
template <class T> using P2 = Point2<T>;

template <ll Mod> struct Modll {
public:
	ll v;
	Modll() : v(0) {}
	Modll(ll _v) { set(_v % Mod + Mod); }
	Modll& set(ll _v) {
		v = (_v < Mod) ? _v : (_v - Mod);
		return *this;
	}
	Modll pow(ll n) const {
		Modll x = *this, ans = 1;
		while (n) {
			if (n & 1) ans *= x;
			x *= x;
			n >>= 1;
		}
		return ans;
	}
	Modll inverse() const { return (*this).pow(Mod - 2); }
	Modll operator+(const Modll& m) const { return Modll().set(v + m.v); }
	Modll operator-(const Modll& m) const { return Modll().set(Mod + v - m.v); }
	Modll operator*(const Modll& m) const { return Modll().set((ull(v) * m.v) % Mod); }
	Modll operator/(const Modll& m) const { return *this * m.inv; }
	Modll& operator+=(const Modll& m) { return *this = *this + m; }
	Modll& operator-=(const Modll& m) { return *this = *this - m; }
	Modll& operator*=(const Modll& m) { return *this = *this * m; }
	Modll& operator/=(const Modll& m) { return *this = *this / m; }
	Modll operator-() const { return Modll(0) - *this; }
	explicit operator bool() const { return v != 0; }
	friend istream& operator>>(istream& in, Modll& m) { return in >> m.v; }
	friend ostream& operator<<(ostream& out, const Modll& m) { return out << m.v; }
};
using mll = Modll<MOD>;
using vmll = V<mll>;
using vvmll = V<vmll>;
using vvvmll = V<vvmll>;

vmll MFactMemo(2, 1);
vmll MIFactMemo(2, 1);

mll mFact(ll n) {
	if (MFactMemo.sz <= n) {
		ll oldsize = MFactMemo.sz;
		MFactMemo.res(n + 1, 1);
		FOR(i, oldsize, n) MFactMemo[i] = MFactMemo[i - 1] * i;
	}
	return MFactMemo[n];
}
mll miFact(ll n) {
	if (MIFactMemo.sz <= n) {
		ll oldsize = MIFactMemo.sz;
		MIFactMemo.res(n + 1, 1);
		MIFactMemo.bk = mFact(n).inv;
		rFOR(i, oldsize + 1, n) MIFactMemo[i - 1] = MIFactMemo[i] * i;
	}
	return MIFactMemo[n];
}
mll mComb(ll n, ll k) {
	if (n < 0 || k < 0 || n < k) return 0;
	return mFact(n) * miFact(k) * miFact(n - k);
}

ll LIS(vll v, ll m = 0) {

	if (v.sz > 0) {
		ll ans = 0;
		vll dp(v.sz, INF);
		FOR(i, 0, v.sz - 1) {
			dp[m ? UPB(dp, v[i]) : LOWB(dp, v[i])] = v[i];
		}
		FOR(i, 0, v.sz - 1) {
			if (dp[i] == INF) break;
			ans++;
		}
		return ans;
	}
	else {
		return 0;
	}

}

ll Bsrch(function<bool(ll x)> f, ll mi, ll ma) {
	ll ng = mi - 1, ok = ma, mid;
	while (ok - ng > 1) {
		mid = (ng + ok) / 2;
		(f(mid) ? ok : ng) = mid;
	}
	return ok;
}

template <class T, class M = decltype(MUL), class S = decltype(ADD)> VV<T> MultiMatrix(VV<T> A, VV<T> B, M Mul = MUL, S Add = ADD) {
	VV<T> ans;
	ll ii = A.sz;
	if (!ii) return ans;
	ll jj = A[0].sz;
	if (!jj) return ans;
	ll jj2 = B.sz;
	if (!jj2) return ans;
	if (jj != jj2) return ans;
	ll kk = B[0].sz;
	if (!kk) return ans;
	ans.asn(ii, V<T>(kk, 0));
	REP(i, ii) {
		REP(k, kk) {
			REP(j, jj) {
				ans[i][k] = Act(Add)(ans[i][k], Act(Mul)(A[i][j], B[j][k]));
			}
		}
	}
	return ans;
}

vvll CombMemo(1000, vll(1000, -1));

ll Comb(ll n, ll k) {
	if ((n < 0) || (k < 0)) return 0;
	if (CombMemo[n][k] == -1) {
		if (n < k) CombMemo[n][k] = 0;
		else {
			if (n == 0) CombMemo[n][k] = 1;
			else if (k == 0) CombMemo[n][k] = 1;
			else if (n == k) CombMemo[n][k] = 1;
			else CombMemo[n][k] = Comb(n - 1, k - 1) + Comb(n - 1, k);
		}
	}
	return CombMemo[n][k];
}

template<class T> map<T, ll> Dict(V<T> v) {
	map<T, ll> m;
	if (!v.sz) return m;
	SORT(v);
	UNIQUE(v);
	REP(i, v.sz) {
		m[v[i]] = i;
	}
	return m;
}

template <class T> vll Cmprs(V<T> v) {
	auto m = Dict(v);
	vll ans(v.sz);
	REP(i,v.sz) {
		ans[i] = m[v[i]];
	}
	return ans;
}

template <class T> vll PCmprs(V<T> v) {
	if (v.sz == 0) return V<T>();
	vll tmp(v.sz);
	vll ans(v.sz);
	IOTA(tmp, 0);
	IOTA(ans, 0);
	sort(tmp.bgn, tmp.en, clam(v[l] < v[r]));
	sort(ans.bgn, ans.en, clam(tmp[l] < tmp[r]));
	return ans;
}

ll BblCnt(vll rv) {
	vll v = PCmprs(rv);
	SegT<ll> b(v.sz, 0);
	ll ans = 0;
	REP(i, v.sz) {
		ans += (i - b.que(0, v[i]));
		b.add(v[i], 1);
	}
	return ans;
}

pl NGrid(pl p, ll i, ll H, ll W) {
	p = mp(p.fi + DX[i], p.se + DY[i]);
	if (p.fi < 0 || p.fi >= H || p.se < 0 || p.se >= W) return mp(INF, INF);
	return p;
}

vvll llGrid(vs v) {
	vvll r(v.sz, vll(v.sz ? v[0].sz : 0, 0));
	REP(h, v.sz) REP(w, v.sz ? v[0].sz : 0) r[h][w] = (v[h][w] == '#');
	return r;
}

template <class T> auto ven(T val) { return val; }
template <> auto ven<int>(int val) { return (ll)val; }
template <class T, class... Args> auto ven(T val, Args... args) {
	auto tmp = ven(args...);
	return V<decltype(tmp)>(val, tmp);
}

template <class T> void zind(T& v) { v--; }
template <class T> void zind(V<T>& v) { ROR(v, i) zind(i); }
template <class T, class... Args> void zind(T& v, Args&... args) { zind(v); zind(args...); }

void Solve();

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout << setprecision(20) << fixed;
	Solve();
}

void Solve() {

	vll c(4, 0);
	UFT t(4);
	ll a, b;
	REP(i, 3) {
		cin >> a >> b;
		zind(a, b);
		c[a]++;
		c[b]++;
		t.merge(a, b);
	}
	ll chk = 1;
	REP(i, 4) {
		REP(j, 4) {
			if (!t.same(a, b)) chk = 0;
		}
	}
	ll gu = 0;
	REP(i, 4) {
		if (c[i] % 2) gu++;
	}
	if ((gu == 0) || (gu == 2)) {

	}
	else {
		chk = 0;
	}
	YN(chk);

}