#include <bits/stdc++.h>
using namespace std;
bitset <1000001> v;
double v2[1000001];
int main()
{
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    v[1]=v[0]=1;
    long long cnt=0,n,sum=0;
    fin>>n;
    for(int i=1;i<=n;i++)
    	v2[i]=i;
    for(double i=2;i<=n;i=i+1)
    	if(v[i]==0)
        {
        	v2[(int)(i)]=i-1;
            for(double j=i+i;j<=n;j+=i)
                v[(int)(j)]=1,v2[(int)(j)]=v2[(int)(j)]*(i-1)/i;
        }
    for(int i=2;i<=n;i++)
        sum=sum+(v2[i]*2);
    fout<<sum+1;
    return 0;