#altERnaTIng cAsE <=> ALTerNAtiNG CaSe
#Define String.prototype.toAlternatingCase (or a similar function/method such as to_alternating_case/toAlternatingCase/ToAlternatingCase in your selected language; 
#see the initial solution for details) such that each lowercase letter becomes uppercase and each uppercase letter becomes lowercase. 
#For example:

#"hello world".toAlternatingCase() === "HELLO WORLD"
#"HELLO WORLD".toAlternatingCase() === "hello world"
#"hello WORLD".toAlternatingCase() === "HELLO world"
#"HeLLo WoRLD".toAlternatingCase() === "hEllO wOrld"
#"12345".toAlternatingCase() === "12345" // Non-alphabetical characters are unaffected
#"1a2b3c4d5e".toAlternatingCase() === "1A2B3C4D5E"
#"String.prototype.toAlternatingCase".toAlternatingCase() === "sTRING.PROTOTYPE.TOaLTERNATINGcASE"

def to_alternating_case(string):
    return ''.join(c.upper() if c.islower() else c.lower() for c in string)   


