import sys

import numpy as np



read = sys.stdin.buffer.read

readline = sys.stdin.buffer.readline

readlines = sys.stdin.buffer.readlines



def main(N):

    div = np.zeros(N+1, np.int64)

    for n in range(1, N+1):

      for m in range(n, N+1, n):

        div[m] += 1

    div *= np.arange(N + 1)

    return div.sum()



if sys.argv[-1] == 'ONLINE_JUDGE':

    import numba

    from numba.pycc import CC

    i8 = numba.int64

    cc = CC('my_module')



    def cc_export(f, signature):

        cc.export(f.__name__, signature)(f)

        return numba.njit(f)



    main = cc_export(main, (i8, ))

    cc.compile()



from my_module import main



N = int(read())

print((main(N)))

import sys

import numpy as np



read = sys.stdin.buffer.read

readline = sys.stdin.buffer.readline

readlines = sys.stdin.buffer.readlines



def main(N):

    div = np.zeros(N+1, np.int64)

    for n in range(1, N+1):

      for m in range(n, N+1, n):

        div[m] += m

    return div.sum()



if sys.argv[-1] == 'ONLINE_JUDGE':

    import numba

    from numba.pycc import CC

    i8 = numba.int64

    cc = CC('my_module')



    def cc_export(f, signature):

        cc.export(f.__name__, signature)(f)

        return numba.njit(f)



    main = cc_export(main, (i8, ))

    cc.compile()



from my_module import main



N = int(read())

print((main(N)))

import sys
import numpy as np

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


def main(N):
    div = np.zeros(N + 1, np.int64)
    for n in range(1, N + 1):
        for m in range(n, N + 1, n):
            div[m] += 1
    div *= np.arange(N + 1)
    return div.sum()


if sys.argv[-1] == "ONLINE_JUDGE":
    import numba
    from numba.pycc import CC

    i8 = numba.int64
    cc = CC("my_module")

    def cc_export(f, signature):
        cc.export(f.__name__, signature)(f)
        return numba.njit(f)

    main = cc_export(main, (i8,))
    cc.compile()
from my_module import main

N = int(read())
print((main(N)))

import sys
import numpy as np

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


def main(N):
    div = np.zeros(N + 1, np.int64)
    for n in range(1, N + 1):
        for m in range(n, N + 1, n):
            div[m] += m
    return div.sum()


if sys.argv[-1] == "ONLINE_JUDGE":
    import numba
    from numba.pycc import CC

    i8 = numba.int64
    cc = CC("my_module")

    def cc_export(f, signature):
        cc.export(f.__name__, signature)(f)
        return numba.njit(f)

    main = cc_export(main, (i8,))
    cc.compile()
from my_module import main

N = int(read())
print((main(N)))

-            div[m] += 1 -    div *= np.arange(N + 1) +            div[m] += m