n=int(input())
a=list(map(int,input().split()))
s=0
for i in range(n-2):
    if a[i]==a[i+2]:
        s+=1
for i in range(n-1):
    if a[i]==a[i+1]:
        s+=1
if s>=1:
    print('Yes')
else:
    print('No')