/*
 * solution by Fredrik Haugen
 */
#include <iostream>  // std::cout
#include <cstdlib>   // std::atol

long long gauss_circle(long r)
{
   long long counted_points = 0;
   long long r2 = r*r;
    
   long y = r - 1;  
   long x = 1;
   while (2 * y*y > r2) 
      if (x*x + y*y <= r2) x++;
      else
      {
         y--;
         counted_points += x-1;
      }

   // exploit symmetry
   return 4 * (2 * counted_points + (y*y + r)) + 1;
}

int main(int argc, char** argv)
{
   long r = std::atol(argv[1]);
   long long N = gauss_circle(r);
   std::cout << N << "\n";
}