#include <stdio.h>

int factorial ( int n )
{
   int prod = 1, i;

   for (i=2; i<=n; ++i) prod *= i;
   return(prod);
}

int binomial ( int n , int r )
{
   return(factorial(n)/(factorial(r)*factorial(n-r)));
}

int main ()
{
   int n, i, s = 0;

   printf("Total number of members : ");
   scanf("%d",&n);
   for (i=2; i<=n/3; ++i) s += binomial(n,i);
   printf("Total number of ways = %d\n", s);
}