// goodwincommaderek@gmail.com
import java.util.Scanner;

public class welcomesign_dg_ac {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int R = in.nextInt();
        int C = in.nextInt();
        StringBuilder sb = new StringBuilder();
        int unevenRows = 0;
        for(int n=0;n<R;n++) {
            String str = in.next();
            int emptySpaces = C - str.length();

            // first, third, fifth, etc rows
            if (unevenRows % 2 == 0) {
                for(int spaceInsertion = emptySpaces/2; spaceInsertion > 0; spaceInsertion--) {
                    sb.append('.');
                }
                sb.append(str);
                for(int spaceInsertion = (emptySpaces+1)/2; spaceInsertion > 0; spaceInsertion--) {
                    sb.append('.');
                }
                sb.append('\n');
            }
            // second, fourth, sixth, etc rows
            else {
                for(int spaceInsertion = (emptySpaces+1)/2; spaceInsertion > 0; spaceInsertion--) {
                    sb.append('.');
                }
                sb.append(str);
                for(int spaceInsertion = emptySpaces/2; spaceInsertion > 0; spaceInsertion--) {
                    sb.append('.');
                }
                sb.append('\n');
            }

            if (emptySpaces % 2 == 1) {
                unevenRows++;
            }
        }
        System.out.print(sb);
    }
}