def ss_to_xy(s: str):
result = re.match(r'<STR_LIT>', s, re.I)<EOL>if result == None:<EOL><INDENT>return None<EOL><DEDENT>xstring = result.group(<NUM_LIT:1>).upper()<EOL>multiplier = <NUM_LIT:1><EOL>x = <NUM_LIT:0><EOL>for i in xstring:<EOL><INDENT>x = x * multiplier + (ord(i) - <NUM_LIT:64>)<EOL>multiplier = multiplier * <NUM_LIT><EOL><DEDENT>x = x - <NUM_LIT:1><EOL>y = int(result.group(<NUM_LIT:2>))-<NUM_LIT:1><EOL>return (x,y)<EOL>
convert spreadsheet coordinates to zero-index xy coordinates.
    return None if input is invalid