#include<stdio.h>    
long n,i;
long v[1000001],s;
FILE*in=fopen("fractii.in","r");
FILE*out=fopen("fractii.out","w");
void verif()
{
    long i,j;
    for(i=2;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i)
        {
            for(j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
        }
}

int main()
{

    fscanf(in,"%ld",&n);
    verif();
    for(i=2;i<=n;i++)
        s=s+2*v[i];
    fprintf(out,"%ld",s+1);
    return 0;
}