#include<stdio.h>
#include<math.h>
int phi[1000005];
void ciur ( int n)
{
    int i,j,lim;
    for(i=1;i<=n;phi[i]=i,i++);
    for(i=2;i<=n;i++)
        if(phi[i]==i)
            for(j=i;j<=n;j=j+i)
                    phi[j]=phi[j]/i*(i-1);
}

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