using System;
using System.Linq;


internal class Program
{
    private static void Main(string[] args)
    {
        var inputArgs = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        var m = inputArgs[0];
        var n = inputArgs[1];
        var integers = Console.ReadLine().Split(' ').Select(int.Parse).Where(x => x > 64 && x < 91).Skip(m).Take(n);
        Console.WriteLine(string.Join("", integers.Select(x => (char) x)));
    }
}