using System;

using System.Collections;

////Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.//

//([)]

//An input string is valid if:

​

//Open brackets must be closed by the same type of brackets.

//Open brackets must be closed in the correct order.

//Every close bracket has a corresponding open bracket of the same type.

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        var str = "{{{}}";

        var result = Checkbrackets(str);

        Console.WriteLine(result);

    }

    public static bool Checkbrackets(string s){

        var stack = new Stack();

        var charArray = s.ToCharArray();

        foreach(var c in charArray){

            if(c == '('){

                stack.Push(c);

            }

            else if (c == '[' ){

                stack.Push(c);

            }

            else if(c == '{' ){

                stack.Push(c);

            }

            else if(c == ')')

            {

                var lat = stack.Peek();

                if(lat.ToString() == "(")

                {

                    stack.Pop();}

                else {return false;}

            }

            else if(c == ']')

            {

                var lat = stack.Peek();

                if(lat.ToString() == "[")

                {

                    stack.Pop();}

                else {return false;}

            }

            else if(c == '}')

            {

                var lat = stack.Peek();

                if(lat.ToString() == "{")

                {

                    stack.Pop();}

                else {return false;}

            }

            else if(stack.Count != 0)

                return false;

        }

        if(stack.Count == 0 )

            return true;

        else return false;

    }

}