#include<cstdio>
using namespace std;
int i,j,n,phi[1000010];
long long 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+=phi[i];
    }
    sol*=2; sol++;
    printf("%lld\n",sol);
    return 0;
}