#include <iostream>
#include <cstdio>

using namespace std;

int a[1000010];
int b[1000010];
int n;

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);

    scanf("%d",&n);

    a[1]=n;
    for(int i=2;i<=n;i++)
    {
        a[i]+=n;
        if(b[i]==0)
        {
            int x=n/i;
            for(int j=i;j<=n;j+=i)
                a[j]-=x-b[j],b[j]++;
        }
    }
    long long s=0;

    for(int i=1;i<=n;i++)
        s+=a[i];

    printf("%lld",s);
    return 0;
}