// Problema fractii ...
// Complexitate O( mai multi n)

#include <stdio.h>
#define MAX       1000001

long d[MAX];

int main()
{
    freopen( "fractii.in", "rt", stdin );
    long n;
         scanf( "%ld", &n );         
    fclose( stdin );
    
    d[1] = 1;
//    d[2] = 3;
    long i, j, k;
    for( i=2; i <=n; i++ )
         {
              k = 0;
           /*   for( j=2; j<=i; j++ )
                   if( i%j != 0 ) k++;
              k = k<<1;*/
              d[i] = d[i-1]+2+tot( i );
         }
         
    freopen( "fractii.out", "wt", stdout );
             printf( "%ld\n", d[n] );
    fclose( stdout );
    
    return 0;
}