#include <stdio.h>
int p[1000000];
 void calc(int n)
 {  
	int i, j,nr2;  
	for (i = 2; i <= n; ++i) 
	{  
		nr2=0;
		if (p[i] == 0) 
		{  
			for (j = i ; j <= n; j += i)
			{  
				nr2++;  
			}	  
			for (j = i ; j <= n; j += i)
			{  
				if (p[j]==0)
					p[j]+=nr2;
				else
					p[j]+=nr2-1;
			}
		}  
	}  
}  
int main()
{
	FILE *in,*out;
	int n,i,nr;
	in=fopen("fractii.in","r");
	out=fopen("fractii.out","w");
	fscanf(in,"%d",&n);
	calc(n);
	nr=n;
	for (i=2;i<=n;i++)
		nr+=n-p[i];
	fprintf(out,"%d\n",nr);
	fclose(in);
	fclose(out);
	return 0;
	
}