def ango(params):
    print(params)
    p = ""
    g = 0
    for name in list(params):
        if name != " ":
            p += chr(int(ord(name)//(2/((g%4)+1))))
        else:
            p+="_"
        g += 1
        
    return p
print(ango('Hello world!'))
print(ango("AAAA"))
print(ango("BBBB"))
print(ango("CCCC"))
print(ango("DDDD"))