n = int(input())
node2con = dict()
con_num = 0
clear = True
for _ in range(n):
    r0, c0, r1, c1 = map(int, input().split())
    if not clear: continue
    is_0 = (r0, c0) in node2con
    is_1 = (r1, c1) in node2con
    if is_0 and is_1:
        clear = False
    elif is_0 and not is_1:
        node2con[r1, c1] = node2con[r0, c0]
    elif is_1 and not is_0:
        node2con[r0, c0] = node2con[r1, c1]
    else:
        node2con[r0, c0] = node2con[r1, c1] = con_num
        con_num += 1
print(['NO', 'YES'][clear])