n = int(input())
a = [int(x) for x in input().split()]
fl = False
for i in range(n-1):
	if a[i] == a[i+1]:
		fl = True
	if 0 < i and a[i-1] == a[i+1]:
		fl = True
	if i < n-2 and a[i] == a[i+2]:
		fl = True

if fl:
	print("Yes")
else:
	print("No")