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

for i in range(N-1):
    if A[i] == A[i+1]:
        print("Yes")
        break
    if 1 <= i and A[i+1] == A[i-1]:
        print("Yes")
        break
    if i+2 < N and A[i] == A[i+2]:
        print("Yes")
        break
else:
    print("No")