list_A="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
list_a=list_A.lower()
list_0="0123456789"

def rot_a(c,k):
    if list_A.find(c) >=0:
        list= list_A
    elif list_a.find(c) >=0:
        list= list_a
    elif list_0.find(c) >=0:
        list= list_0
    else:
        return c

    l = len(list)
    position = list.find(c)
    p= (position + k) % l
    return list[p]

def rot(c,k):
    l=len(c)
    p=""
    for i in range(l):
        p+=rot_a(c[i],k)
    return p