#include<bits/stdc++.h>
using namespace std;
unsigned long long pr[500005],eu[500005],qz[500005],pn;
bool p[500005];
void euler(int n)
{
    long long k=0;
    eu[1]=1;
    for(int i=2;i<=n;++i)
    {
        if(!p[i])pr[++pn]=i,eu[i]=i-1;
        for(int j=1;j<=pn&&k<=n;++j)
        {
            k=i*pr[j];
            p[k]=1;
            if(i%pr[j]==0)
            {
                eu[k]=eu[i]*pr[j];
                break;
            }
            eu[k]=(pr[j]-1)*eu[i];
        }
    }
}
int main()
{
    euler(40000);
    for(int i=1;i<=40000;++i)
        qz[i]=qz[i-1]+eu[i];
    int n;
    cin>>n;
    if(n==1)cout<<0;
    else cout<<qz[n-1]*2+1;
    return 0;
}