#include <cstdio>
#include <iostream>
using namespace std;
int v[1000001],p[1000001];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n,i,j;
    long long Ans=0;
    scanf("%d", &n);
    for(i=2;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
    {
        if(!p[i])
        {
            for(j=i;j<=n;j+=i)
            {
                p[j]=1;
                v[j]/=i;
                v[j]*=i-1;
            }
        }
        Ans+=v[i];
    }
    cout<<1+(Ans<<1);
    return 0;
}