#include <stdio.h>
#include <stdlib.h>
int countDominoWays(int numOfLevelLeft);
int main()
{
  printf("Number of ways to fill the board = %d \n",countDominoWays(20));
  return 0;
}
int countDominoWays(int numOfLevelLeft)
{
  if(numOfLevelLeft == 0) // No place left on board
    return 0;
  if(numOfLevelLeft == 1) // only one way to fill last level ( -- )
    return 1;
  
  // Board can be filled in two types of domino placement ( -- ) or ( || )
  // ( -- ) uses one level on board ( || ) uses 2 level on board
    
  return countDominoWays(numOfLevelLeft - 1) + countDominoWays(numOfLevelLeft - 2);
}