using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var strings = new List<string>() { "012abc", "120ccc", "000aaa" };

        var arrays = strings.Select(x => x.ToCharArray());

        var charResult = arrays.Aggregate((a, b) => b.ToList().Select((t,i) => (char)Math.Max(t, a[i])).ToArray());

        Console.Write(new string(charResult.ToArray()));

    }

}