#include <cstdio>
using namespace std;

int n,s[1000001];
unsigned long long suma;

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