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