#K,Q=map(int, input().split())
N=int(input())
A=list(map(int, input().split()))

A.append(-1)
A.append(-2)
ans='No'
for i in range(N):
  if A[i]==A[i+1]:
    ans='Yes'
  if A[i]==A[i+2]:
    ans='Yes'
print(ans)