#include<stdio.h>
#define input "fractii.in"
#define output "fractii.out"
#define dim 101
long long unsigned n,a[dim];
int main()
{
    freopen(input,"r",stdin);
    freopen(output,"w",stdout);
    long long unsigned s=0,i,j;
    scanf("%llu",&n);
    for(i=2;i<=n;i++)
    if(!a[i])
    {
             s+=(i-1);
             for(j=2*i;j<=n;j+=i)
             if(!a[j])
             a[j]=j-j/i;
             else
             a[j]-=a[j]/i;
    }
    else
    s+=a[i];
printf("%llu",2*s+1);
return 0;
}