爱因斯坦台阶问题：有人走一台阶，若每步走两级则最后剩一级；若每步走三级则最后剩两级；若每步走四级则最后剩三级；若每步走五级则最后剩四级；若每步走六级则最后剩五级；若每步走七级则刚好不剩，问台阶共有几级？-Einstein level problem: Some people take a step, if each step taking two of the last remaining one if each of the last remaining step is to go thr