#define maxn 1000002
#include<cstdio>

using namespace std;

int a[maxn];

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