import java.io.PrintStream;
import java.nio.BufferOverflowException;
import java.util.HashMap;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Scanner;

import type.lib.CharStack;

public class Check11D
{
    public static void main(String[] args)
    {
	Scanner input = new Scanner(System.in);
	PrintStream output = System.out;

	output.println("Enter expression");
	String expression = input.nextLine();

	Map<Character, Character> opposite = new HashMap<Character, Character>();
	opposite.put(')', '(');
	opposite.put(']', '[');
	opposite.put('}', '{');

	try
	{
	    CharStack stack = new CharStack();
	    for (int i = 0; i < expression.length(); i++)
	    {
		char letter = expression.charAt(i);
		if (opposite.containsValue(letter))
		{
		    stack.add(letter);
		} 
		else if (opposite.containsKey(letter))
		{
		    char top = stack.removeLast();
		    if (top != opposite.get(letter))
		    {
			throw new Exception("Overlapping");
		    }
		}
	    }

	    if (!stack.isEmpty())
	    {
		throw new Exception("Imbalanced");
	    }

	    output.println("OK");
	}
	catch (BufferOverflowException e)
	{
	    output.println("Too deeply nested");
	}
	catch (NoSuchElementException e)
	{
	    output.println("Imbalanced");
	}
	catch (Exception e)
	{
	    output.println(e.getMessage());
	}
    }
}