N=int(input())
A=list(map(int,input().split()))
if N==2:
    ans=A[0]==A[1]
elif N==3:
    ans=A[0]==A[2]
else:
    ok=False
    for i in range(N-1):
        if A[i]==A[i+1]:
            ok=True
    for i in range(N-2):
        if A[i]==A[i+2]:
            ok=True
    ans=ok
print('Yes' if ok else 'No')