数乌龟

public class Wg {

public static void main(String[] args) {


int[] arr = new int[100];
arr[0] = 0;
arr[1] = 1;
arr[2] = 2;
arr[3] = 3;
for(int i=4;i<arr.length;i++){
arr[i] = arr[i-1] + arr[i-3];
}

System.out.println(arr[6]);
}

}