#include<stdio.h>
long long unsigned n,i,j,s,a[2000000],k;
int main()
{
FILE *f=fopen("fractii.in","r"), *g=fopen("fractii.out","w");
fscanf(f,"%llu",&n);
for(i=2;i<=n;++i)
	if (a[i]==0)
		    for (j=i*2;j<=n;j=j+i)
					if (j%i==0)
						   {   if (a[j]==0)
							 a[j]=j;
						      a[j]=a[j]-a[j]/i;
						      }


for (i=1;i<=n;++i)
    if (a[i]==0)
       s=s+i-1;
       else s=s+a[i];
fprintf(g,"%llu",s*2+1);
return 0;
}