using System;

using System.Collections.Generic;

using System.Linq;

public class SmallestMultiple

{

​

    // Find the smallest multiple of the given list:

    public static long FindSmallestMultiple(List<int> numList)

    {

        if (numList == null || numList.Count == 0)

        {

            return 0;

        }

​

        var result = (long)numList[0];

​

        for (int i = 1; i < numList.Count; i++)

        {

            result = Lcm(result, numList[i]);

        }

​

        return result;

    }

    // Gets the Least common multiple of two longs.

    public static long Lcm(long a, long b)

    {

        return Math.Abs(a * b) / Gcd(a, b); 

    }

    public static long Gcd(long a, long b)

    {

        while (a != 0)

        {

            var temp = a;

            a = b % a;

            b = temp;

        }

        return b;

    }

​

    public static void Main(string[] args)

    {

        var gcd1 = Gcd(8, 32);

        Console.WriteLine($"The GCD of 8 and 32 is:\n {gcd1}");

        var listNums1 = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

        var listNums2 = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 };

        long smallestMultipleToTen = FindSmallestMultiple(listNums1);

        long smallestMultipleToTwenty = FindSmallestMultiple(listNums2);        

        var stringNum1 = string.Join(", ", listNums1);

        var stringNum2 = string.Join(", ", listNums2);

        Console.WriteLine($"The smallest multiple of {stringNum1} is:\n {smallestMultipleToTen}");

        Console.WriteLine($"The smallest multiple of {stringNum2} is:\n {smallestMultipleToTwenty}");

    }

}