#include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define REP(i,n) for(int i=0; i=b; --i) #define ALL(c) (c).begin(), (c).end() typedef long long ll; typedef vector VI; typedef vector VL; typedef vector VVI; typedef pair P; typedef pair PL; map f, a; VI check, x, y, d; bool pos; int dx[] = {-1,1,0,0}, dy[] = {0,0,1,-1}; void dfs(int id, int xc, int yc, int c){ if (check[id]) return; check[id] = 1; int x1, x2, y1, y2; x1 = x[id], y1 = y[id]; if (d[id] == 0) x2 = x1 + 1, y2 = y1; else x2 = x1, y2 = y1 + 1; if (x1 == xc && y1 == yc){ a[P(x1,y1)] = c; a[P(x2,y2)] = c^1; REP(k,4){ int xx = x1 + dx[k], yy = y1 + dy[k]; if (xx == x2 && yy == y2) continue; if (f[P(xx,yy)] == 0) continue; int id_next = f[P(xx,yy)] - 1; if (check[id_next] && a[P(xx,yy)] != c) pos = false; dfs(id_next, xx, yy, c); } REP(k,4){ int xx = x2 + dx[k], yy = y2 + dy[k]; if (xx == x1 && yy == y1) continue; if (f[P(xx,yy)] == 0) continue; int id_next = f[P(xx,yy)] - 1; if (check[id_next] && a[P(xx,yy)] == c) pos = false; dfs(id_next, xx, yy, c^1); } } if (x2 == xc && y2 == yc){ a[P(x2,y2)] = c; a[P(x1,y1)] = c^1; REP(k,4){ int xx = x2 + dx[k], yy = y2 + dy[k]; if (xx == x1 && yy == y1) continue; if (f[P(xx,yy)] == 0) continue; int id_next = f[P(xx,yy)] - 1; if (check[id_next] && a[P(xx,yy)] != c) pos = false; dfs(id_next, xx, yy, c); } REP(k,4){ int xx = x1 + dx[k], yy = y1 + dy[k]; if (xx == x2 && yy == y2) continue; if (f[P(xx,yy)] == 0) continue; int id_next = f[P(xx,yy)] - 1; if (check[id_next] && a[P(xx,yy)] == c) pos = false; dfs(id_next, xx, yy, c^1); } } } int main() { int t; t = 1; while (t--){ int n; cin >> n; pos = true; f.clear(); a.clear(); check.clear(); check.resize(n); x.resize(n); y.resize(n); d.resize(n); REP(i,n){ char c; int x1, x2, y1, y2; cin >> x1 >> y1 >> x2 >> y2; if (x1 > x2) swap(x1, x2); if (y1 > y2) swap(y1, y2); x[i] = x1; y[i] = y1; if (x1 < x2) c = 'x'; else c = 'y'; f[P(x[i], y[i])] = i+1; if (c == 'x') f[P(x[i]+1, y[i])] = i+1, d[i] = 0; else f[P(x[i], y[i]+1)] = i+1, d[i] = 1; } REP(i,n){ if (!check[i]) dfs(i, x[i], y[i], 1); // REP(j,n) cout << check[j]; // cout << endl; } // REP(i,4){ // REP(j,4){ // cout << f[P(i,j)]; // } // cout << endl; // } // cout << endl; // REP(i,4){ // REP(j,4){ // cout << a[P(i,j)]; // } // cout << endl; // } cout << (pos ? "YES" : "NO") << endl; } return 0; }