#include <iostream>
#include <fstream>
#define inFile "fractii.in"
#define outFile "fractii.out"

using namespace std;

int v[1000003];

int main()
{
    long long n,i,j,s=0;

    ifstream fin(inFile);
    fin>>n;
    fin.close();


    for(i=1;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i)
            for(j=2*i;j<=n;j+=i)
            {
                v[j]/=i,v[j]*=(i-1);
            }

    s+=n;

    for(i=2;i<=n;i++)
        s+=v[i];

    ofstream fout(outFile);
    fout<<s;
    fout.close();
}