#include <iostream>
#include <cstdio>
using namespace std;
long long int n,p=1;
int a[1000001];

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%lld",&n);
    for(int i=1;i<=n;i++)
        a[i]=i-1;
    for(int j=4;j<=n;j+=2)
        a[j]-=a[2];
    for(int i=3;i<=n;i+=2)
    {
        a[i]=i-1;
        for(int j=i+i;j<=n;j+=i)
            a[j]-=a[i];
    }
    for(int i=1;i<=n;i++)
        p+=2*a[i];

    printf("%lld",p);
    return 0;
}