MIT Interview Question 2 Marks - Time 30 seconds

def fun(s):
    k=len(s)
    m=''
    for i in range(0,k):
        if(s[i].isupper()):
            m=m+s[i].lower()
        elif(s[i].isalpha()):
            m=m+s[i].upper()
        else:
            m=m+'bb'
    print(m)
fun('@gmail.com')

# Answer: bbGMAILbbCOM