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

int cmmdc(int a,int b)
{
	int c;
    while (b) {
        c = a % b;
        a = b;
        b = c;
    }
    return a;
}



int main()
{

	FILE *file;
	int n,i,nr;

	file = fopen("fractii.in","r");

	fscanf(file,"%d",&n);

	fclose(file);

	nr = n * n;
	nr -= n / 2;
	nr++;
	nr -= (n / 2)*(n / 2);

	for(i = 3;i <= n/2;i = i + 2)
	{
		if(n / i != 1)
		{
			nr -= (n / i - 1) * n / i;		
		}
	}

	file = fopen("fractii.out","w");
	fprintf(file,"%d",nr);
	fclose(file);

}