#include <fstream>

using namespace std;

int n,a[1000003];

int main()
{
    int i,j;
    ifstream fin("fractii.in");
    fin>>n;
    for(i=1;i<=n;++i)   a[i]=i-1;
    for(i=2;i<=n;++i)
        for(j=2*i;j<=n;j+=i)
            a[j]-=a[i];
    long long s=1;
    for(i=1;i<=n;++i)
        s+=2LL*a[i];
    ofstream fout("fractii.out");
    fout<<s<<"\n";
    fout.close();
    return 0;
}