輸入描述：

多行輸入，一行輸入一個int型整數表示第n個月

輸出描述：

每一行輸出對應的兔子總數

示例1

1
2
3
4
5
9

1
1
2
3
5
34

 1 import java.io.BufferedReader;
 2 import java.io.InputStreamReader;
 3 import java.io.IOException;
 4 
 5 public class Main {
 6     public static void main(String[] args) throws
 
 IOException {
 7         BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 8         String line;
 9         while((line = br.readLine()) != null) {
10             int n = Integer.parseInt(line);
11             int mount1 = 1;  //1月兔子
12             int mount2 = 0;  //2月兔子
13             int
 
 mount3 =0;  //3月兔子
14             int add = 0;  //下個月將出生的兔子
15             for(int i = 2; i <= n; i++) {  //從2月開始計算，i表示第i個月
16                 mount3 = mount3 + mount2;
17                 mount2 = mount1;
18                 mount1 = add;
19                 add = mount2 + mount3;
20             }
21             System.out.println(mount1 + mount2 + mount3);
 
22         }
23     }
24 }