Java代码
import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
System.out.println(f(n));
}
public static int f(int n){
if(n <= 3){
return n;
}
return f(n - 1) + f(n - 2);
}
}