#include <stdio.h>
using namespace std;
int phi[1000001];
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n,i,j;
    long long nr_fractii = 1;
    scanf("%d",&n);
    for(i=2;i<=n;i++)
        phi[i] = i-1;
    for(i=2;i<=n;i++){
        for(j=2*i;j<=n;j+=i)
            phi[j] -= phi[i];
    }
    for(i=2;i<=n;i++)
        nr_fractii += phi[i]*2;
    printf("%lld",nr_fractii);
    return 0;
}