k = value of rotation
s = input string
====================
def caesarCipher(s, k):
st=""
for i in s:
if i>='a' and i<='z':
if ord(i)+k <=122:
st+=chr(ord(i)+k)
else:
st+=chr(ord(i)+k-122+96)
elif i>='A' and i<='Z':
if ord(i)+k <=90:
st+=chr(ord(i)+k)
else:
st+=chr(ord(i)+k-90+64)
else:
st+=i
return st