#include <stdio.h>


int prim(long int x){
	long int i;
	if (x==2)
		return 1;
	if (x%2==0)
		return 0;
	for (i=3;i*i<=x;i+=2)
		if (x%i==0)
			return 0;
	return 1;
}


long int n_div(long int x){
	long int i,aux;
	aux=0;
	for (i=2;i<x;i++)
		if(x%i==0)
			aux++;
	return aux;
}

int main(){
	long int N,x,i;
	int aux;
	FILE *fin,*fout;
	fin=fopen("fractii.in","rt");
	fout=fopen("fractii.out","wt");

	fscanf(fin,"%ld",&N);

	x=1;
	for (i=2;i<=N;i++){
		if (prim(i)==1)
			x+=2*(i-1);
		else {
			aux=n_div(i);
			x+=2*(i-aux-1);
		}
	}

	fprintf(fout,"%ld",x);

	fclose(fout);
	fclose(fin);
	return 0;
}