#include <bits/stdc++.h> using namespace std; typedef signed long long ll; #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x<(to);x++) #define FORR(x,arr) for(auto& x:arr) #define FORR2(x,y,arr) for(auto& [x,y]:arr) #define ALL(a) (a.begin()),(a.end()) #define ZERO(a) memset(a,0,sizeof(a)) #define MINUS(a) memset(a,0xff,sizeof(a)) template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;} template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;} //------------------------------------------------------- int M; int A[101010],B[101010],C[101010]; map<pair<int,int>,vector<int>> V; map<pair<int,int>,int> D; void dfs(pair<int,int> p,int dir) { if(D.count(p)) { if(D[p]!=dir) { cout<<"NO"<<endl; exit(0); } return; } D[{p.first,p.second}]=dir; D[{p.second,p.first}]=dir^1; if(V[p].size()>2) { cout<<"NO"<<endl; exit(0); } FORR(v,V[p]) { if(p.first==A[v]&&p.second==B[v]||p.first==B[v]&&p.second==C[v]||p.first==C[v]&&p.second==A[v]) { dfs({A[v],B[v]},dir); dfs({B[v],C[v]},dir); dfs({C[v],A[v]},dir); } else { dfs({A[v],B[v]},dir^1); dfs({B[v],C[v]},dir^1); dfs({C[v],A[v]},dir^1); } } } void solve() { int i,j,k,l,r,x,y; string s; cin>>M; vector<int> Xs; FOR(i,M) { cin>>A[i]>>B[i]>>C[i]; Xs.push_back(A[i]); Xs.push_back(B[i]); Xs.push_back(C[i]); } sort(ALL(Xs)); FOR(i,M) { A[i]=lower_bound(ALL(Xs),A[i])-Xs.begin(); B[i]=lower_bound(ALL(Xs),B[i])-Xs.begin(); C[i]=lower_bound(ALL(Xs),C[i])-Xs.begin(); V[{A[i],B[i]}].push_back(i); V[{B[i],C[i]}].push_back(i); V[{C[i],A[i]}].push_back(i); V[{B[i],A[i]}].push_back(i); V[{C[i],B[i]}].push_back(i); V[{A[i],C[i]}].push_back(i); } FORR2(a,b,V) if(D.count(a)==0) dfs(a,0); cout<<"YES"<<endl; } int main(int argc,char** argv){ string s;int i; if(argc==1) ios::sync_with_stdio(false), cin.tie(0); FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin); cout.tie(0); solve(); return 0; }