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

int N, A[1000005];
long long cnt;

int main(void)
{
    int i, j;

    freopen("fractii.in", "r", stdin);
    scanf("%d", &N);

    for (i = 0; i < N; i++) A[i + 1] = i;

    for (i = 2; i <= N; i++)
    for (j = i << 1; j <= N; j += i)
        A[j] -= A[i];

    for (cnt = 1, i = 2; i <= N; i++)
        cnt += (long long) (A[i] << 1);

    freopen("fractii.out", "w", stdout);
    printf("%lld\n", cnt);

    return 0;
}