#include #define rep(i, ss, ee) for (int i = ss; i < ee; ++i) using namespace std; using P = pair; //(2,8),(3,9),(7,9) //(5,8),(4,8),(6,8) void solve() { int N, k; map m{{{2, 8}, 3}, {{3, 9}, 6}, {{7, 9}, 9}}; vector

e{{5, 8}, {4, 8}, {6, 8}}; P p, q; cin >> N; rep(i, 0, N) { cin >> p.first >> p.second >> q.first >> q.second; k = m[p]; m[q] = k; m.erase(p); } string ans = "YES"; rep(i, 0, 3) if (m[e[i]] != (i + 1) * 3) ans = "NO"; cout << ans << endl; } int main() { cin.tie(0); ios::sync_with_stdio(false); solve(); getchar(); }