N = int(input())
a_list = list(map(int, input().split()))

is_true = False
for n in range(N - 1):
	if n == N - 2:
		if a_list[n] == a_list[n + 1]:
			is_true = True
	else:
		if a_list[n] == a_list[n + 1] or a_list[n] == a_list[n + 2]:
			is_true = True

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