using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] array = { 2, 3, 4, 2, 1, 3, 4 };
        Dictionary<int, int> frequencyMap = new Dictionary<int,

 int>();

        foreach (int num in array)
        {
            if (frequencyMap.ContainsKey(num))
            {
                frequencyMap[num]++;
            }
            else
            {
                frequencyMap[num] = 1;
            }
        }

        foreach (KeyValuePair<int, int> entry in frequencyMap)
        {
            Console.WriteLine(entry.Key + " -> " + entry.Value);
        }
    }
}