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