import re

def substitute_digits(input_string):
    def replace_digit(match):
        digits = match.group()
        replaced_digits = ''
        for digit in digits:
            if '0' <= digit <= '9':
                replaced_digits += chr(ord('a') + int(digit))
            else:
                replaced_digits += digit
        return replaced_digits

    pattern = re.compile(r'\d{4}')
    substituted_string = pattern.sub(replace_digit, input_string)

    return substituted_string


file_path = 'simple.in'
with open(file_path, 'r', encoding = 'utf-8') as file:
    for line in file:
        line = line.rstrip('\n')
        result = substitute_digits(line)
        print(result)