#include<stdio.h>
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
char viz[1000000];
long v[20000],n,k;
long long x;

void ciur()
{
k=0;
  for(long i=2;i<=n;i++)
    if(!viz[i])
    {++k;v[k]=i;
     for(long j=i+i;j<=n;j+=i)
	 viz[j]=1;
    }

}

void solve()
{
 x=n*n-(n-1);
 long t; 
  
  for(long i=1;i<=k;i++)
    {
     t=n/v[i]-1;
     if(t>0)
       x-=t*(t+1);         

    }

}


int main()
{
fscanf(f,"%ld",&n);

x=0;
ciur();
solve();

fprintf(g,"%lld",x);
return 0;

}