#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define REP(i, n) for (int (i) = 0; (i) < (n); (i)++) #define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++) #define RREP(i, a) for(int (i) = (a) - 1; (i) >= 0; (i)--) #define FORR(i, a, b) for(int (i) = (a) - 1; (i) >= (b); (i)--) #define DEBUG(C) cerr << #C << " = " << C << endl; using LL = long long; using VI = vector; using VVI = vector; using VL = vector; using VVL = vector; using VD = vector; using VVD = vector; using PII = pair; using PDD = pair; using PLL = pair; using VPII = vector; template using VT = vector; #define ALL(a) begin((a)), end((a)) #define RALL(a) rbegin((a)), rend((a)) #define SORT(a) sort(ALL((a))) #define RSORT(a) sort(RALL((a))) #define REVERSE(a) reverse(ALL((a))) #define MP make_pair #define FORE(a, b) for (auto &&a : (b)) #define FIND(s, e) ((s).find(e) != (s).end()) #define EB emplace_back template inline bool chmax(T &a, T b){if (a < b){a = b;return true;}return false;} template inline bool chmin(T &a, T b){if (a > b){a = b;return true;}return false;} const int INF = 1e9; const int MOD = INF + 7; const LL LLINF = 1e18; const int SIZE = 120; int N; VVI graph(SIZE * SIZE); bool dame = false; bool used[SIZE * SIZE]; PII ip(int n) { return MP(n / SIZE, n % SIZE); } int pi(PII p) { return p.first * SIZE + p.second; } int pi(int r, int c) { return pi(MP(r, c)); } int cnt = 0; void dfs(int st, int now, int prev = -1) { cnt += used[now]; if (cnt >= 2) { dame = true; return; } if (used[now]) return; used[now] = true; FORE(e, graph[now]) if (e != prev) { dfs(st, e, now); } } int main(void) { memset(used, false, sizeof(used)); scanf("%d", &N); REP(i, N) { int a, b, c, d; scanf("%d%d%d%d", &a, &b, &c, &d); a--;b--;c--;d--; //cout<= 2) { cout << "NO" << endl; return 0; } } cout << "YES" << endl; }