#!/usr/bin/env python3

########################################################################
##
##  fletcher4.py
##
##  Copyright (C) 2024 Herbert Poetzl
##
##
##  This program is free software; you can redistribute it and/or modify
##  it under the terms of the GNU General Public License version 2 as
##  published by the Free Software Foundation.
##
########################################################################

import sys
import struct

a = b = c = d = 0
# Read bytes directly from stdin
while True:
    byte_block = sys.stdin.buffer.read(4)
    if not byte_block:
        break

    value = struct.unpack('I', byte_block)[0]
    
    a += value;
    b += a;
    c += b;
    d += c;

a &= 0xFFFFFFFF
b &= 0xFFFFFFFF
c &= 0xFFFFFFFF
d &= 0xFFFFFFFF

r = ((a ^ c) << 32) ^ b ^ d

# Print the final sum
print(f"{r:016X}")