N = int(input())
ans = 0
for i in range(1, N):
    b = N % i
    if b == 0:
        b = i
    a = (N - b) // i - b
    if a <= 0:
        break
    c = - N % (i + 1)
    if c == 0:
        c = i + 1
    d = (N + c) // (i + 1) - c
    if d <= 0:
        break
    ans += (a + b) - (c + d) + 1
print(ans)