Tiling

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 6746		Accepted: 3291

Description

In how many ways can you tile a 2xn rectangle by 2x1 or 2x2 tiles? 

Here is a sample tiling of a 2x17 rectangle. 

Input

Input is a sequence of lines, each line containing an integer number 0 <= n <= 250.

Output

For each line of input, output one integer number in a separate line giving the number of possible tilings of a 2xn rectangle. 

Sample Input

2812100200

Sample Output

317127318451004001521529343311354702511071292029505993517027974728227441735014801995855195223534251

Source

 

import java.util.*;import java.math.*;public class Main{    public static void main(String[] args){        Scanner cin=new Scanner(System.in);        int n;        while(cin.hasNext()){            n=cin.nextInt();            if(n==0){                System.out.println("1");                continue;            }else if(n==1){                System.out.println("1");                continue;            }else if(n==2){                System.out.println("3");                continue;            }                            BigInteger a=BigInteger.valueOf(1);            BigInteger b=BigInteger.valueOf(3);            BigInteger c;            for(int i=3;i<=n;i++){                c=b.add(a.multiply(BigInteger.valueOf(2)));                a=b;                b=c;            }            System.out.println(b);        }    }}