#include <stdio.h>
#include <stdlib.h>
int v[1000001];
int main() {
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    int n;
    int i, j;
    scanf("%d",&n);
    for (i = 2; i <= n; i++) {
        v[i] = i;
    }
    i = 2;
    while (i <= n) {
        for (j = i; j <= n; j+=i) {
            v[j] /= i;
            v[j] *= (i - 1);
        }
        while (v[i] != i && i <= n)
            i++;
    }
    unsigned long long nr = 0;
    for (i = 1; i <= n; i++)
        nr += v[i];
    nr= 2 * nr + 1;
    printf("%llu",nr);
    return 0;
}