#include <cstdio>
#define lld long long unsigned
#define N 1000005
using namespace std;
lld sol;
int n,i,j,a[N];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(i=2;i<=n;i++)
        a[i]=i-1;
    for(i=2;i<=n;i++)
    {
        sol+=a[i];
        for(j=2*i;j<=n;j+=i)
            a[j]-=a[i];
    }
    sol*=2;sol++;
    printf("%lld",sol);
    return 0;
}