#include <stdio.h>
FILE *in,*out;

int v[1000100];

int main(){
    in=fopen("fractii.in","r");
    out=fopen("fractii.out","w");

    int i,n,j;
    fscanf(in,"%d",&n);
    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*(i-1);
    int sum=0;
    for(i=1;i<=n;i++)
        sum+=v[i];
    fprintf(out,"%d",sum*2-1);
    fclose(out);
    fclose(in);
}