#include <stdio.h>

long long i,j,sum,n;
long long phi[1000010];

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