#include <stdlib.h>
#include <stdio.h>
#define nmax 1000005
int n;
long long sol;
int v[nmax];
int main()
{
    int i,j;
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    scanf("%d", &n);
    sol=1;
    for (i=2; i<=n; i++)
        v[i]=i-1;
    for (i=2; i<=n; i++)
    {
        for (j=2*i; j<=n; j+=i)
            v[j]-=v[i];
        sol+=1LL*(v[i]<<1);
    }
    printf("%d",sol);
    return 0;
}