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

long long int fi(int n)
{
    long long int result = n, i;
    for(i=2;i*i <= n;i++)
    {
        if (n % i == 0) result -= result / i;
        while (n % i == 0) n /= i;
    }
    if (n > 1) result -= result / n;
    return result;
}

int main()
{
    int i;
    int n;
    long long int count;
    FILE *f, *g;

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

    count = -1;

    for(i=0;i<n;i++)
    {
        count+=2*fi(i+1);
    }
    g = fopen("fractii.out", "wt");
    fprintf(g, "%lli", count);
    fclose(g);
    printf("%lli", count);




    return 0;
}