package cn.io.com;

public class DiGui {

	public static void main(String[] str) {
		/*int[] arr=new int[20];
		arr[0]=1;
		arr[1]=1;
		arr[2]=arr[0]+arr[1];
		
		for (int x=2;x<arr.length;x++) {
			arr[x]=arr[x-2]+arr[x-1];
		}
		//System.err.println(arr[19]);
		int a=1;
		int b=1;
		for(int x=0;x<18;x++){
			int temp=a;
			a=b;
			b=temp+a;
		}
		System.err.println(b);*/
		System.out.println(fib(20));
	}

	private static int fib(int n) {
		if(n ==1 || n ==2){
			return 1;
		}else {
			return fib(n-1)+fib(n-2);
		}
		
	}
    
}