#include<cstdio> 
#define N 1000001 
long long s=0,e[N]; 
long long  i,n; 
void era(int n) 
{     
long long i,j;     
for(i=2;i<=n;++i)         
e[i]=i;     
for(i=2;i<=n;++i)         
if(e[i]==i)         
for(j=i;j<=n;j=j+i)             
e[j]=e[j]/i*(i-1); } 
int main() 
{     
freopen("fractii.in","r",stdin);     
freopen("fractii.out","w",stdout);          
scanf("%lld",&n);     
era(n);     
for(i=2;i<=n;++i)         
s+=e[i];     
printf("%lld",2*s+1);     
return 0; 
}