#include <fstream>
#include <bitset>

using namespace std;
ifstream f ("fractii.in");
ofstream g ("fractii.out");
long long n,k,i,j,e[101001],s;
///bitset<2000050> p;

int main()
{
    f>>n;
    for(i=2;i<=n;i++)
        e[i]=i;
    for(i=2;i<=n;i++)
        if(e[i]==i){
        for(j=i;j<=n;j+=i)
            e[j]=e[j]/i*(i-1);
        }
    for(i=2;i<=n;i++)
    {
        s=s+e[i];
    }
    g<<s*2+1;
    return 0;
}