#include<algorithm>
#define DIM 1000001
using namespace std;
int n,c[DIM];
void ciur(){
    int i,j;
    for(i=2; i<=DIM; ++i)
        c[i]=i;
    for(i=2; i<=DIM; ++i)
        if(c[i]==i)
            for(j=i; j<=DIM; j+=i)
                c[j]=c[j]/i*(i-1);}
void solve(){
    int i;
    long long s;
    scanf("%d",&n);
    for(i=2,s=0; i<=n; ++i)
        s+=c[i];
    printf("%lld",2*s+1);}
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    ciur();
    solve();
    return 0;}