void node_add(struct node *tree,int b){
        struct node *add=new struct node;
        while(true){
                if(b>=tree->val){
                        if(tree->right==NULL){
                                tree->right=add;
                                add->val=b;
                                add->left=NULL;
                                add->right=NULL;
                                break;
                        }
                        else    tree=tree->right;
                }
                else{
                        if(tree->left==NULL){
                                tree->left=add;
                                add->val=b;
                                add->left=NULL;
                                add->right=NULL;
                                break;
                        }
                        else    tree=tree->left;
                }
        }
        return;
}