def transform st for in range len st st if len st st len st return

def transform(st):
    r = ''
    for i in range(len(st)/5):
        q = st[i*5:(i+1)*5]
        r += q[4]+q[0]+q[3]+q[1]+q[2];
    if len(st)%5:
        r += st[-(len(st)%5):]
    return r