You are given a positive integer n greater or equal to 2. For every pair of integers a and b (2 ≤ |a|, |b| ≤ n), you can transform a into b if and only if there exists an integer x such that 1 < |x| and (a ⋅ x = b or b ⋅ x = a), where |x| denotes the absolute value of x.

After such a transformation, your score increases by |x| points and you are not allowed to transform a into b nor b into a anymore.

Initially, you have a score of 0. You can start at any integer and transform it as many times as you like. What is the maximum score you can achieve?

Input

A single line contains a single integer n (2 ≤ n ≤ 100 000) — the given integer described above.

Output

Print an only integer — the maximum score that can be achieved with the transformations. If it is not possible to perform even a single transformation for all possible starting integers, print 0.

Examples

Input

4


Output

8

Input

6


Output

28

Input

2


Output

0

Note

In the first example, the transformations are 2 → 4 → (-2) → (-4) → 2.

In the third example, it is impossible to perform even a single transformation.
from collections import defaultdict, Counter,deque
from math import sqrt, log10, log, floor, factorial,gcd
from bisect import bisect_left, bisect_right
from itertools import permutations,combinations
from heapq import heapify,heappop,heappush
import sys, io, os
input = sys.stdin.readline
input=io.BytesIO(os.read(0,os.fstat(0).st_size)).readline
# sys.setrecursionlimit(10000)
inf = float('inf')
mod = 10 ** 9 + 7
def get_list(): return [int(i) for i in input().split()]
def yn(a): print("YES" if a else "NO")
ceil = lambda a, b: (a + b - 1) // b
t=1
for i in range(t):
    n=int(input())
    suma=0
    for j in range(2,n+1):
        for k in range(2*j,n+1,j):
            suma+=k//j
    print(suma*4)



