LazyK (incomplete)

LazyK.py

import re, sys

def lex(s):
    for m in re.finditer(r'S|I|K|\(|\)', s):
        yield m.group(0)

def parse(s):
    l = lex(s)
    while True:
        x = next(l)
        if x == '(':
            yield parse_chunk(l)
        else:
            yield x
    
def parse_chunk(l):
    x = '('
    i = 1
    while i:
        x += next(l)
        if x[-1] == ')':
            i -= 1
        if x[-1] == '(':
            i += 1
    return x

def run(s):
    a = list(parse(s))

    try:
        if a[0] == 'I':
            return run(a[1])
        elif a[0] == 'K':
            return run(a[1])
        elif a[0] == 'S':
            x = "({0} {2}) ({1} {2})"
            return run(x.format(a[1],a[2],a[3]))
        else:
            a[0] = a[0][1:-1]
            return run(''.join(a))
    except:
        return s

print(run(input()))