import copy
N = int(input())
sosu = [2]
nums = list(range(3,N+1,2))
while 1:
    tmp = copy.deepcopy(nums)
    if len(nums)==0:
        break
    sosu.append(nums[0])
    div = nums[0]
    for i in range(len(nums)):
        try:
            if nums[i]%div==0:
                nums.pop(i)
                i-=1
        except IndexError:
        	break
    if tmp==nums:
        break
if N==1:
    print(0)
elif N==2:
    print(1)
else:
    print(sum(sosu)+sum(nums))