public static int sockMerchant(int n, List ar) { int pairCount = 0; Dictionary DictionaryObj = new Dictionary();

    foreach (var item in ar)
    {
        if (DictionaryObj.ContainsKey(item))
        {
            DictionaryObj[item]++;
        }
        else
        {
            DictionaryObj[item] = 1;
        }
    }

    foreach (int count in DictionaryObj.Values)
    {
        pairCount += count / 2;
    }
    return pairCount;
}****