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

ans = 0
left = 0
while left < N:
    right = left + 1
    if right < N and A[left] + 1 == A[right]:
        right += 1
        while right < N and A[right-1] + 1 == A[right]:
            right += 1
        tmp = right - left
        ans += tmp * (tmp - 1) // 2
        left = right
    elif right < N and A[left] - 1 == A[right]:
        right += 1
        while right < N and A[right - 1] - 1 == A[right]:
            right += 1
        tmp = right - left
        ans += tmp * (tmp - 1) // 2
        left = right
    else:
        left += 1
print(ans)