def group_when(xs, pred):
    res = []
    a = []
    for x in xs:
        if not a or pred(a[-1], x):
            a.append(x)
        else:
            res.append(a)
            a = [x]
    if a:
        res.append(a)
    return res


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

gg = group_when(A, lambda a, b: a+1 == b)
ans = 0
for g in gg:
    k = len(g)
    ans += k * (k - 1) // 2

print(ans)