百度之星资格赛 2016 Problem 1002

 1 import java.util.Scanner;
 2 import java.math.BigInteger;
 3 
 4 public class Main{
 5     public static void main(String[] args){
 6         Scanner sc = new Scanner(System.in);
 7         while(sc.hasNextInt()){
 8             int n = sc.nextInt();
 9             BigInteger a1 = new BigInteger("1");
10             BigInteger a2 = new BigInteger("2");
11             BigInteger ans = new BigInteger("0");
12             for(int i = 3; i <= n; i++){
13                 ans = a1.add(a2);
14                 a1 = a2;
15                 a2 = ans;
16             }
17             if(n == 1)System.out.println("1");
18             else if(n == 2)System.out.println("2");
19             else    System.out.println(ans.toString());
20         }
21         sc.close();
22     }
23 }