#include <iostream>
#include <fstream>
using namespace std;

int n,i,j,v[1000005];

long long s=1;

int main(void){
    ifstream f("fractii.in");
ofstream g("fractii.out");
    f>>n;

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