using System;
using System.Collections;
using System.Linq;
using System.Text;

namespace Snake_Moves
{
    class SnakeMoves
    {
        static void Main(string[] args)
        {
            int[] inputDimention = Console.ReadLine().Split(' ', StringSplitOptions.RemoveEmptyEntries).Select(int.Parse).ToArray();

            int row = inputDimention[0];
            int col = inputDimention[1];

            char[,] matrix = new char[row, col];

            StringBuilder snake = new StringBuilder(Console.ReadLine());

            if (snake.Length > 0)
            {
                int r = 0;
                int c = 0;

                for (int i = 0; i < (row * col); i++)
                {
                    char sh = snake[0];
                    snake.Remove(0, 1);
                    snake.Append(sh);

                    matrix[r, c] = sh;

                    if (r % 2 == 0)
                    {
                        c++;
                    }
                    else
                    {
                        c--;
                    }

                    if (c == col)
                    {
                        c--;
                        r++;
                    }

                    if (c < 0)
                    {
                        c++;
                        r++;
                    }
                }
            }// if (snake.Length > 0

            StringBuilder temp = new StringBuilder();

            snake.Clear();
            for (int r = 0; r < row; r++)
            {
                temp.Clear();
                for (int c = 0; c < col; c++)
                {
                    temp.Append($"{matrix[r, c]}");
                }
                snake.AppendLine(temp.ToString());
            }

            Console.WriteLine(snake.ToString());
        }
    }
}