#include<stdio.h>
#include<string.h>
#define dim 1000001
using namespace std;
int a[dim];
int main()
{long long n,i,k,j;
 FILE*f=fopen("fractii.in","r");
 FILE*g=fopen("fractii.out","w");
 
 fscanf(f,"%lld",&n);
 
 for(i=1;i<=n;i++)
	 a[i]=i;
 
 for(i=2;i<=n;i++)
	 if(a[i]==i)
		 for(j=1;j*i<=n;j++)
			 a[j*i]=a[j*i]*(i-1)/i;
 
 k=0;
 for(i=1;i<=n;i++)
	 k+=a[i];
 	
 fprintf(g,"%lld\n",k*2-1);
 fclose(f);
 fclose(g);
 return 0;
}