N=int(input())
A=list(map(int,input().split(" ")))

flag=False

if N==2 and A[0]==A[1]:
  flag=True

for i in range(0,N-1):
  if i != N-2 and A[i]==A[i+2] or A[i]==A[i+1]:
    flag=True
    break

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