In this problem, we want to remove all occurrences of a space-seperated key in a string. This problem can be solved using the replace() function, as well as a few other string functions. First, check if the string contains " " + key + " ", if it does, replace it with a single space. Next, check if the start or end contains the key separated by a space. If it does, remove the key. However, we cannot check the substring if the key and string have the same length as we will get an index out of bounds exception, so we check if the key and string are the same length first. Finally, check if the key and string are equal to each other. If they are, print an empty string.

Pseudocode:

s,key = input()
while(s.contains(" " + key + " "):
    s.replace(" " + key + " ", " ")
if(len(s) > len(key):
    if(s.substring(0,len(key)+1) == key + " "):
        s = s.substring(len(key)+1,len(s))
    if(s.substring(len(s)-len(key)-1, len(s)) == " " + key):
        s = s.substring(0, len(s)-len(key)-1)
if(s == key)
    s = ""
print(s)