import re


def decode(code: str) -> str:
    """If there are symbols or spaces between two alphanumeric characters
    of the decoded script, then the function replaces them with a single space ''
    for better readability.
    The function doesn't use 'if' conditions for decoding.
    Alphanumeric characters consist of: [A-Z, a-z, and 0-9].
    >>> decode("This$#is% Matrix#  %!")
    This is Matrix#  %!
    >>> decode("This%%isMatrix#scrpt&%!&")
    This isMatrix scrpt&%!&
    """
    # Define a regular expression pattern to match non-alphanumeric characters
    # between alphanumeric characters
    pattern = r"(?<=[a-zA-Z0-9])[^a-zA-Z0-9]+(?=[a-zA-Z0-9])"

    # Use re.sub() to replace matched patterns with a single space
    decoded = re.sub(pattern, " ", code)

    # Return the decoded string
    return decoded


# Read the number of rows and columns from input
rows, columns = map(int, input().split())

# Read the matrix of characters row by row
matrix_dec, str_decoded = [input() for _ in range(rows)], ""

# Iterate through columns and rows to create a string by combining characters from the matrix
for col in range(columns):
    for row in range(rows):
        str_decoded += matrix_dec[row][col]

# Print the result of decoding the created string
print(decode(str_decoded))