#include<cstdio>
using namespace std;
int i,j,n,phi[1000010],sol;
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++) phi[i]=i-1;
    for(i=2;i<=n;i++)
        for(j=2*i;j<=n;j+=i) phi[j]-=phi[i];
    sol=1;
    for(i=2;i<=n;i++) sol+=2*phi[i];
    printf("%d\n",sol);
}