BASE64 Encoding

Given a string S, write a program that prints the BASE64 encoding of S.

BASE64 encoding walks the input three bytes at a time from the front. It cuts the 24 bits of each group into four pieces of 6 bits, then turns the value of each piece, a number between 0 and 63, into one character by this rule.

• 0 through 25 become 'A' through 'Z'
• 26 through 51 become 'a' through 'z'
• 52 through 61 become '0' through '9'
• 62 becomes '+', and 63 becomes '/'

If the last group holds fewer than three bytes, pad it with zero bits to fill out the 6 bit pieces, and write '=' at every piece position that no input byte reached. One leftover byte adds two '=' characters and two leftover bytes add one. The length of the encoded result is therefore always a multiple of 4.

The first line contains the string S. S consists of uppercase letters, lowercase letters, and digits only, and its length is between 1 and 50.

Print the BASE64 encoding of S on the first line.