Competitions

# Binary Search Tree 1

Implement a balanced binary search tree.

#### Input

Contains the description of operations on the tree, their number is not greater than 105. Each line contains one of the next operations:

• insert x - add the key x into the tree. If the key x is already in the tree, do nothing.
• delete x - delete the key x from the tree. If the tree does not contain the key x, do nothing.
• exists x - if the key x is in the tree, print "true", otherwise print "false".

All numbers are integers not greater than 109 by absolute value.

#### Output

Print the result of all operations exists in format given in sample output.

Time limit 3 seconds
Memory limit 128 MiB
Input example #1
insert 2
insert 5
insert 3
exists 2
exists 4
delete 5

Output example #1
true
false