#include<cstdio>
using namespace std;
unsigned i,j,s,n,v[1000000];
//FILE *f1,*f2;
int main()
{
    //freopen("fractii.in","r",stdin);
    scanf("%u",&n);
    for(i=2;i<=n;i=i+1)
    v[i]=i-1;
    for(i=2;i<=n;i++)
    {
        if(v[i]==i-1)
        {
            for(j=2*i;j<=n;j=j+i)
            v[j]=v[j]-v[i];
        }
    }
    for(i=2;i<=n;i++)
    s=s+v[i];
    s=2*s+1;
    //freopen("fractii.out","w",stdout);
    printf("%u\n",s);
    return 0;
}