n=input()
a=[raw_input()for i in range(n)]
s=None
for i in range(n):
	a=sorted(a,key=lambda x:-a.count(x))
	for j in range(len(a)):
		if s!=a[j]:
			s=a[j]
			a.pop(j)
			break
	else:
		print"NO"
		break
else:
	print"YES"