#include <cstdio>
using namespace std;

FILE *f=fopen ("fractii.in","r");
FILE *g=fopen ("fractii.out","w");

bool ap[1000002];

long long phi(int n){
	
	if (!ap[n]) return 1LL*(n-1);
	
    long long p=n;
    for (long long d=2;d*d<=n;++d){
        if (n%d==0){
            p=p*(d-1)/d;
            while (n%d==0) n/=d;
        }
    }
    if (n!=1) p=p*(n-1)/n;
    return p;
}

void ciur (int n){
	for (int i=2;i<=n;++i){
		if (!ap[i]){
			for (int j=i+i;j<=n;j+=i) ap[j]=1;
		}
	}
}


int main(){
	int n;
	long long s=0;
	
	fscanf (f,"%d",&n);
	
	ciur (n);
	
	for (int i=2;i<=n;++i) s+=phi(i);
	
	fprintf (g,"%lld",2*s+1);
	
	return 0;
}