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