#include<stdio.h>
long long int phi[1000001];
int main(){

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

	long long int n,i,j,sol=0;
	fscanf(f,"%ld",&n);
	
	for(i=1;i<=n;i++) phi[i]=i-1;
	for(i=2; i<= n>>1 ; i++)
		for(j=i<<1 ; j<=n; j+=i) phi[j] -= phi[i];
	for(i=2;i<=n;i++) sol += phi[i]<<1;
	fprintf(g,"%lld",sol+1);
	return 0;
}