# include <stdio.h>
# include <math.h>

# define IN "fractii.in"
# define OUT "fractii.out"
# define NMAX 1000001

int nr[NMAX],N;
int i,j;


void gasestePrime();
long long int tot(int n);

int main (){
	FILE *in=fopen(IN,"rt");
	fscanf(in,"%d",&N);
	fclose(in);
	
	FILE *out=fopen(OUT,"wt");
	long long int sum=1;
	if(N!=1)
		for (i=2;i<=N;i++)
			nr[i]=i-1;
	for (i = 2; i <= N; ++i)
    	for (j = 2*i; j <= N; j += i)
        	nr[j] -= nr[i];
        	
    for (i=2;i<=N;i++)
    	sum+=2*nr[i];
    
    fprintf(out,"%lld",sum);
    fclose(out);
    return 0;	
}