// filling the blocks according to given specification

#include<stdio.h>
int fillblocks(int n){
	if (n==1) return 1;//base cases
	if (n==2) return 2;//base cases
	else return fillblocks(n-1) +fillblocks(n-2);// this is recursive because if we put one block vertically then n-1x2 will remain to be filled and if we put 2                                                       blocks horizontally then n-2x1 will be remaining to fill.
	return 1;
}

int main(){
	int n=20;
	int no_of_ways= fillblocks(n);
	printf("Number of ways to arrange the blocks in a board of size %d x 2 is %d. \n", n, no_of_ways);
	return 0;
}