10198 - Counting/Main.java

   1 import java.io.*;
   2 import java.math.*;
   3
   4 public class Main{
   5     public static void main(String args[]) throws Exception{
   6         BufferedReader cin = new BufferedReader(new InputStreamReader(System.in));
   7
   8         BigInteger dp[] = new BigInteger[1010];
   9         for (int i=0; i<1010; ++i) dp[i] = BigInteger.ZERO;
  10         dp[0] = BigInteger.ONE;
  11         for (int i=0; i<=1000; ++i){
  12             dp[i+1] = dp[i+1].add(dp[i]);
  13             dp[i+1] = dp[i+1].add(dp[i]);
  14             dp[i+2] = dp[i+2].add(dp[i]);
  15             dp[i+3] = dp[i+3].add(dp[i]);
  16         }
  17         String s;
  18         while ((s = cin.readLine()) != null){
  19             System.out.println(dp[Integer.parseInt(s)].toString());
  20         }
  21     }
  22 }