c#

public static string canConstruct(List a)

{
// Return "Yes" or "No" denoting whether you can construct the required number.
    string answer = "No";
    var digits = new List<int>();
    for (int i = 0; i < a.Count; i++)
    {
        while (a[i] > 0)
        {
            digits.Add(a[i]%10);
            a[i] /= 10;
        }
    }
    int sumList = digits.Sum();
    if (sumList % 3 == 0)
    {
        answer = "Yes";
    }
    return answer;
}