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

int v[1000001];

int main() {
    int n, i, j;
    long long nr_sol;
    FILE *fin, *fout;

    fin=fopen("fractii.in", "r");
    fscanf(fin, "%d", &n);
    fclose(fin);

    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);
            }
        }
    }

    nr_sol = 1;
    for(i = 2; i <= n; i++)
        nr_sol += v[i] * 2;

    fout=fopen("fractii.out", "w");
    fprintf(fout, "%lld", nr_sol);
    fclose(fout);

    return 0;
}