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

for i in range(N - 1):
    B = A[:]
    B[i], B[i + 1] = B[i + 1], B[i]

    for j in range(N - 1):
        if B[j] == B[j + 1]:
            print("Yes")
            exit()

print("No")