a="ABCDEFGHIJKLMNOPQRSTUVWXYZ"

p=input("Plain text: ").upper().replace(" ","")
k=input("Key: ").upper().replace(" ","")
e="".join(a[(a.index(p[i])+a.index(k[i%len(k)]))%26] for i in range(len(p)))
print("Encrypted:",e)

c=input("Cipher text: ").upper().replace(" ","")
d="".join(a[(a.index(c[i])-a.index(k[i%len(k)]))%26] for i in range(len(c)))
print("Decrypted:",d)