import sys


def solve():
    N = int(input())
    c2n = dict()
    node_n = 0
    Adj = []

    for i in range(N):
        r0, c0, r1, c1 = map(int, input().split())

        if (r0, c0) not in c2n:
            c2n[r0, c0] = node_n
            node_n += 1
            Adj.append([])
        if (r1, c1) not in c2n:
            c2n[r1, c1] = node_n
            node_n += 1
            Adj.append([])

        u = c2n[r0, c0]
        v = c2n[r1, c1]
        Adj[u].append(v)
        Adj[v].append(u)

    remove_deg1(node_n, Adj)

    for u in range(node_n):
        if len(Adj[u]) > 2:
            print('NO')
            break
    else:
        print('YES')


def remove_deg1(node_n, Adj):
    for u in range(node_n):
        if len(Adj[u]) == 1:
            v = Adj[u].pop()
            Adj[v].remove(u)

            while len(Adj[v]) == 1:
                u = v
                v = Adj[v].pop()
                Adj[v].remove(u)

    return None


def debug(x, table):
    for name, val in table.items():
        if x is val:
            print('DEBUG:{} -> {}'.format(name, val), file=sys.stderr)
            return None

if __name__ == '__main__':
    solve()