There is a string a (unknown to you), consisting of lowercase Latin letters, encrypted according to the following rule into string s : after each character of string a , an arbitrary (possibly zero) number of any lowercase Latin letters, different from the character itself, is added; after each such addition, the character that we supplemented is added. You are given string s , and you need to output the initial string a . In other words, you need to decrypt string s . Note that each string encrypted in this way is decrypted uniquely.

To decrypt string s, you can iterate through each character of s and group together all the characters that belong to the same character in the original string a. To do this, you can keep track of the current character being processed and a count of the number of additional characters that have been added after it. Whenever a new character is encountered, it means that the previous group of characters (including the current character and its additional characters) belong to one character in the original string a. So you can add the current character to the decrypted string a, and reset the count and current character to the new character.

Here's the Python code to implement this:

def decrypt_string(s):
    a = ''
    curr_char = ''
    count = 0
    for c in s:
        if c != curr_char:
            a += curr_char
            curr_char = c
            count = 1
        else:
            count += 1
        if count > 1:
            a += c
    a += curr_char
    return a

For example, if s = 'aabbccdd', the function will return 'abcd'.