规则：
% (1)正在燃烧的树变成空格位；
% (2)如果绿树格位的最近邻居中有一个树在燃烧，则它变成正在燃烧的树；
% (3)在空格位，树以概率p生长；
% (4)在最近的邻居中没有正在燃烧的树的情况下树在每一时步以概率f(闪
%　　 电)变为正在燃烧的树。
% 参考文献:
% 祝玉学，赵学龙译，<<物理系统的元胞自动机模拟>>, p23(Rule:
% (1) the burning trees turn into spaces;
% (2) if the nearest neighbor sites in the trees have a tree in the burning, it becomes a burning tree;
% (3) in spaces, and trees grow in probability p;
% (4) in the nearest neighbor, there is no burning tree in the case of the tree at each step, with probability f (flashing)
% electricity) into a burning tree.
% references:
% Zhu Yuxue, translated by Zhao Xuelong, the "physical simulation system of cellular automaton, p23)