#include<stdio.h>

int main()
{
    FILE *fin,*fout;
    long n,i,j,s=0;
    long v[1000001];

    fin=fopen("fractii.in","rt");
    fscanf(fin,"%ld",&n);
    fclose(fin);

    for(i=1;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;
                v[j]=v[j]*(i-1);
            }
    for(i=1;i<=n;i++)
        s+=v[i];


    fout=fopen("fractii.out","wt");
    fprintf(fout,"%ld",2*s-1);
    fclose(fout);



    return 0;
}