#include<stdio.h>
int main()
{
	FILE *f,*q;
	int n, i,j,x,v[100005];
	long long int cont = 1;
	f = fopen("fractii.in", "a+t");
	q = fopen("fractii.out", "wt");
	if (f == NULL)
	{
		exit(0);

	}
	else
	{
		fscanf(f, "%d", &n);
		for (i = 2; i <= n; ++i)
			v[i] = i;

		for (i = 2; i <= n; ++i) {
			if (v[i] == i)
				for (j = i; j <= n; j+= i)
					v[i] = v[i] / i * (i - 1);
			cont = cont + v[i] * 2;
		}
				
			
		fprintf(q,"%d\n", cont);
	}
	system("pause");
	return 0;
}