n = input()
xs = {}
ys = {}
for _ in xrange(n):
    curx, cury = map(int,raw_input().split())
    if curx in xs:
        xs[curx] += 1
    else:
        xs[curx] = 1
    if cury in ys:
        ys[cury] += 1
    else:
        ys[cury] = 1
        
vals = xs.values()
vals.extend(ys.values())
        
for val in vals:
    if val == n:
        print 'YES'
        exit()
        
print 'NO'