#include <cstdio>

int n,i,j,euler[1000001];
long long sol;

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for (i=2; i<=n; i++)
        euler[i]=i-1;
    for (i=2; i<=n; i++)
    {
        sol=sol+euler[i];
        for (j=2*i; j<=n; j=j+i)
            euler[j]=euler[j]-1;//euler[i];
    }
    printf("%lld\n",2*sol+1);
    return 0;
}