import sys
input = sys.stdin.readline

n=int(input())
A=list(map(int,input().split()))

flag=0

for i in range(n-1):
    if A[i]==A[i+1]:
        flag=1
    if i+2<n and A[i]==A[i+2]:
        flag=1

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