#include <iostream>
#include <cstdio>
#define nmax 1000001
FILE * f = fopen("fractii.in", "r");
FILE * g = fopen("fractii.out", "w");
using namespace std;
 
 int phi[nmax];
int main( ) {
    int n;
    fscanf(f,"%d", &n);
    for (int i = 1; i <= n; ++i)
    phi[i] = i-1;
for (int i = 2; i <= n; ++i)
    for (int j = 2*i; j <= n; j += i)
        phi[j] -= phi[i];
    int i  ;
    long int result1 = 1;
 
    for(i=2;i<=n;i++)
         result1 = result1 + 2 * phi[i];
    fprintf(g,"%ld",result1);
    fclose(f);
    fclose(g);
    return 0;
}