#include<stdio.h>
#include<stdlib.h>


FILE * fp;
FILE * fp2;
fp = fopen("fractii.in","r+");
fp2 = fopen("fractii.out","w+");

long long r;
int N,j,n,nr,i,a[2000010];
int main()
{
    fscanf(fp,"%d",&N);
    for (i=2;i<=N;i++)
        a[i] = i;
    for (i=2;i<=N;i++)
        if(a[i]==i)
        {
            for(j= i;j<=N;j+=i)
                a[j]=a[j]/i*(i-1);
        }
    for (i=1;i<=N;i++)
        r+=a[i];
    r=r*2;
    r+=1;
    fprintf(fp2,"%d",r);
    return 0;
}