#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n,i,j,v[1000005];

unsigned long long s=1;

int main(void){
    fin>>n;

    for (i=2;i<=n;i++)
        v[i]=i-1;
    for (i=2;i<=n;i++){
        s+=2*v[i];
        for(j=2*i;j<=n;j+=i)v[j]-=v[i];
    }
    fout<<s;
    return 0;
}