// Fractii.cpp : Defines the entry point for the console application.
//

#include <stdio.h>
#include <stdlib.h>

int cmmdc(int a, int b)
{
	int r;
	r = a%b;
	while (r != 0)
	{
		a = b;
		b = r;
		r = a % b;
	}
	return b;
}

int main(int argc, char* argv[])
{
    int n;
    int i, j;
    FILE *f1, *f2;
	double l;
	long long sum = 0;
	double *a;
	char *sel;

    f1 = fopen("fractii.in", "r");
    f2 = fopen("fractii.out", "w");

    if (f1 == NULL || f2 == NULL)
    {
        return 0;
    }

	if (fscanf(f1, "%d", &n) <= 0)
	{
		fclose(f1);
		return 0;
	}


	a = (double *) malloc(sizeof(double) * n);
	sel = (char *) malloc(sizeof(int) * n);
	for (i = 0; i < n; i++)
	{
		a[i] = i + 1;
		sel[i] = 0;
	}
	
	for (i = 1; i < n; i++)
	{
		if (sel[i] == 0)
		{
			l = 1 - (double) 1 / (i+1);
			a[i] *= l;
			for (j = 2*(i+1); j <= n; j += (i+1))
			{																	
				a[j-1] *= l;
				sel[j-1] = 1;
			}			
		}
	}

	for (i = 0; i < n; i++)
	{
		sum += a[i] * 2;
	}
	sum = sum - 1; // 1/1 era pus de 2 ori

	fprintf(f2, "%lld", sum);
	return 0;
}