def solve():
    n = int(input())
    A = [0] + list(map(int, input().split())) + [0]
    B = [0] * (n + 2)
    for i in range(2, n + 1):
        if A[i - 1] == A[i]:
            B[i - 1] = B[i] = 1
    C = B[:]
    for i in range(1, n + 1):
        if B[i - 1] + B[i] + B[i + 1] == 0:
            B[i] = 1
    for i in range(2, n + 1):
        if C[i - 1] + C[i] + C[i + 1] == 0:
            C[i] = 1
    print(max(sum(B), sum(C)))
solve()