#include <stdio.h>
int main(){
	FILE*in  = fopen("fractii.in", "r");
	FILE*out = fopen("fractii.out","w");
	long i,n,j,phi[1000000] = {0};
	long long s = 1;
	fscanf ( in, "%ld", &n);

	for ( i = 1; i <= n; ++i)
	    phi[i] = i-1;
	for ( i = 2; i <= n; ++i)
	    for ( j = 2*i; j <= n; j+=i)
		phi[j] -= phi[i];

	for ( i = 2; i <= n;i++)
	    s += 2*phi[i];
	fprintf (out, "%lld", s);
	return 0;
}