using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Dictionary<int,string> dict = new Dictionary<int,string>();

        AddDict(dict,1,"Mk");

        AddDict(dict,2,"Mks");

        AddDict(dict,3,"Mk");

        AddDict(dict,2,"Mks");      

    }

    static void AddDict(Dictionary<int,string> dic,int key,string value)

    {

        if(!dic.ContainsKey(key))

        {

            dic.Add(key,value);

            Console.WriteLine($"Added key {key} and {value}");              

        }

        else {

            Console.WriteLine($"Duplicate key {key}");

        }

    }

}