#include<cstdio>
FILE *in,*out;
using namespace std;
unsigned long long Scai[999999];
unsigned long long i,j,N;
int main()
{
    in=fopen("fractii.in","rt");
    fscanf(in,"%llu ",&N);
    fclose(in);
    for (i=2;i<=N;i++)
        Scai[i]=i-1;
    for (i=2; i<=N; i++)
        for (j=2*i; j<=N; j+=i)
            Scai[j]=Scai[j]-Scai[i];
    unsigned long long raspuns=1;
    for (i=2; i<=N; i++)
        raspuns+=(Scai[i]*2);
    out=fopen("fractii.out","wt");
    fprintf(out,"%llu", raspuns);
    fclose(out);
    return 0;
}