In edge we have two endpoints, and there is no comment, that first is parent, second is son. May be (and it's really true) that first is son, and second is parent. Program without this remark gets WA (I checked it). My first solution with remark about it AC. And without expressions about 0-apple nodes; in condition we have no phrases about it; People, who wrote something about ingnoring zero-nodes are wrong.

Thank you!!! :-) Now I have AC!!!