#include <iostream>

using namespace std;

int main() {

  long long i,j,r,n;

  cout<<"r = ";  cin>>r;

  i=r; j=1; n=0;

  while (i>=1) {

      while (i*i+j*j<=r*r) j=j+1;

      n=n+r-j+1;

      i--;

  }

  n=2*(2*r+1)-1+4*r*r-n*4;

  cout<<n<<endl;

  system("pause");

  return(0);

}