/*
TASK:necklace
LANG:C++
*/

# include <iostream.h>

int main ()
{
   int b;
   cin >> b;
   if (b==1 ) cout << "0";
   if (b==2) cout <<"0";
   if (b==3) cout << "1";
      
   if (b==5) cout << "7";
   if (b==4) cout << "2";
   if (b==6) cout << "11";
   if (9 <= b <= 11) cout << (b-1)*2+2;
   if (12<= b <= 14) cout <<  (b-1)*2+3;
   if (15 <= b <= 17) cout << (b-1)*2+4;
   if (18 <= b <= 20)cout << (b-1)*2+5;
   if (21 <= b <= 23) cout << (b-1)*2+6;
   if (24 <= b <= 26)cout << (b-1)*2+7;
   if (27<= b <= 29)cout << (b-1)*3+8;
  return 0;

}


