Given is a positive integer N. How many tuples (A,B,C) of positive integers satisfy A \times B + C = N?

Constraints

* 2 \leq N \leq 10^6
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N


Output

Print the answer.

Examples

Input

3


Output

3


Input

100


Output

473


Input

1000000


Output

13969985
n = int(raw_input())
ans = 0
def f(a,n):
	howmanybs = n/a
	return howmanybs +(-1 if n % a == 0 else 0)

for a in xrange(1, n+1):
	ans += f(a,n)
print ans