key="CIPHERKEY"
 
Cipher="This Is The Cipher Text"
 
str("Decrypt")
temp=0
lengthkey=len(key)
length=len(Cipher)
 
for i in range(length):
    if(temp<=lengthkey):
        Decrypt=(Cipher[i]-key[temp])%26
        temp+=1
    if (temp>lengthkey):
        temp=0
print Decrypt