public void deleteByNumberOfBlocks(StudentsTree tree,int num) {
        BSTNode nodetoremove= deleteByNumberOfBlocks(num, tree.root );
        tree.removeStudent(nodetoremove.oStudent.email);
    }
        public BSTNode deleteByNumberOfBlocks( int n, BSTNode node) {

            if (node != null) {
                if (node.oStudent.blocks>= n) {
                    return node;
                }else {
                    BSTNode foundNode = deleteByNumberOfBlocks(n, node.left);
                    if (foundNode != null) {
                        return foundNode;
                    }return deleteByNumberOfBlocks(n, node.right);
                }
            }
                    return null;
        }