#include <cstdio>

using namespace std;

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    long long s=0;
    int n;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        s=s+i*(n/i);
    s=s*2;
    printf("%lld",s);
    return 0;
}