#include <cstdio>
using namespace std;
const int N=1000000;
int n;
int v[N+5];
long long sol;
void build(){
    int i,j;
    for(i=1;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++){
        if(v[i]==i)
            for(j=i;j<=n;j=i+j){
                v[j]=v[j]/i;
                v[j]=v[j]*(i-1);
            }
        sol=sol+v[i];
    }
}
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    int i;
    build();
    printf("%lld",2*sol+1);
    return 0;
}