import math

n = int(input())
a = [0]*10**7
x = math.sqrt(10)
b = math.floor(x)
l = 0
for i in range(1,n+1):
  x = math.sqrt(i)
  b = math.floor(x)
  for j in range(1,b+1):
    if(i%j==0 and i//j == j):
      a[i-1] +=1
    elif(i%j==0):
      a[i-1] +=2
for k in range(n):
  l = l + a[k]*(k+1)
print(l)
 
