using System;

using Newtonsoft.Json.Linq;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var json = @"{

""stores"": [

{

            ""ID"": 17736791,

""Name"": ""ABC""

},

{

            ""ID"": 154423041,

""Name"": ""XYZ""

}

],

""product"": [

{

""ID"": 154423041,

""Amount"": 19865337

}

]

}";

        var obj = JObject.Parse(json);

        var storeIds = obj["stores"]

            .Select(s => (int)s["ID"])

            .ToList();

        var selectedAmount = obj["product"]

            .Where(p => storeIds.Contains((int)p["ID"]))

            .Select(p => (int)p["Amount"])

            .FirstOrDefault();

        Console.WriteLine(selectedAmount);

    }

}