#include<stdio.h>
int v[1000000];
int main()
{
    FILE *fin,*fout;
    fin=fopen("fractii.in","r");
    fout=fopen("fractii.out","w");
    int n;
    fscanf(fin,"%d",&n);
    int i;
    for(i=2;i<=n;i++)
        v[i]=i-1;
    long long sol=0;
    for(i=2;i<=n;i++)
    {
        sol+=v[i];
        int cont,var=v[i];
        for(cont=i;cont<=n;cont+=i)
            v[cont]-=var;
    }
    fprintf(fout,"%lld",sol*2+1);
    fclose(fin);
    return 0;
}