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

for i in range(N-1):
    A[i],A[i+1] = A[i+1],A[i]
    flag = False
    for j in range(N-1):
        if(A[j] == A[j+1]):flag = True
    if(flag):
        print("Yes")
        exit()

    A[i],A[i+1] = A[i+1],A[i]
print("No")