#include<cstdio>
#define nmax 1000010
using namespace std;
long long n,i,j,v[nmax], sol,nr;
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%lld", &n);
    for(i=2;i<=n;++i)
        if(!v[i])
        {
            nr=0;
            for(j=i+i;j<=n;j+=i)
                v[j]+=++nr;
        }
    for(i=n;i>1;--i)
        sol+=(i-1-v[i]);
    printf("%lld", 2*sol+1);
    return 0;
}