//窮舉
public class Exhaustion {
	
	public static void main(String args[]) {
		Exhaustion e = new  Exhaustion();
				System.out.println(e.cal(100, 300));
	}
	
	public String cal(int heads, int legs) {
		for(int i =0; i < heads; i++) {
			if(i*2+(heads-i)*4 ==legs) {
				return "chiken: "+i+" rabbit: "+(heads-i);
			}
		}
		return "null";
		
		
	}

}
 

//遞迴 遞推
//求階乘 求數列

public class Recursion {
	public static void main(String args[]) {
		Recursion e = new  Recursion();
				System.out.println(e.Fibonacci(35));				
				System.out.println(e.jiecheng(2));
				
	}
	//Fibonacci
	public int Fibonacci(int length) {
		if(length <= 2) {
			return 1 ;
		}else {
			int a = Fibonacci(length - 2);
			int b = Fibonacci(length - 1);
			return a+b;
		}
	}
	
	//求n！
	//n！=n*(n-1)(n-2)*...*2*1
	//(n-1)! = (n-1)(n-2)*...*2*1
	//n! = n*(n-1)!
	public int jiecheng(int n) {
		if(n <= 2) {
			return n*1;
		}else{
			return n*jiecheng(n-1);
		}
	}
}