def main():
    n,l=map(int,raw_input().split())
    #print n
    #print l

    r = 0 #result
    p = 0 #previous
    q = 0 #current

    b = [] #buffer
    for c in sys.stdin.read(): #character
        if c == ' ':
            q = int(''.join(b))
            b = []
            r += q ^ p #yes there is a bug with A[0] but lets optimize the loop for now
            p = q
        else:
            b.append(c)
    r += int(''.join(b)) ^ p

    print r
main()

import re
import sys

from collections import deque

def main():
    n,l=map(int,raw_input().split())
    #print n
    #print l

    r = 0
    p = 0
    q = 0

    b = sys.stdin.read(l)

    b = deque(b.rsplit(' ',4000000))
    n = len(b)
    while n == 4000001:
        c = b.popleft()
        b = map(int,b)
        for i in xrange(n-2,0,-1):
            r += b[i] ^ b[i-1]

        m = b[0]
        b = deque(c.rsplit(' ',3999999))
        b.append(m)
        n = len(b)


    b = map(int,b)
    for i in xrange(n-1,0,-1):
        r += b[i] ^ b[i-1]

    print r
main()

f = open("digits.txt", "rb")
try:
    bytes = []
    previous_num = None
    byte = f.read(1)
    while byte != "":
        if byte != " ":
            bytes.append(byte)
        else:
            # convert bytes to a number and reset list
            current_num = int(''.join(map(str, bytes)))
            if not previous_num:
                previous_num = current_num
            else:
                # do your operation on previous and current number
            bytes = []
        byte = f.read(1)
finally:
    f.close()

#!python2.7
from __future__ import print_function
import os, time

numbers = "100 69 38 24 17 11 3 22 "
print("Numbers:", numbers)


if not os.path.isfile('numbers.txt'):
    with open('numbers.txt', 'w') as outfile:
        n = 7*1000*1000
        print("Repeating %d times..." % n)
        print(numbers * n, file=outfile)

print("Starting read. Time:", time.strftime("%c"))
total = 0
with open('numbers.txt') as f:
    prv = None
    for nxt in f.read().split():
        nxt = int(nxt)
        if prv is not None:
            total += prv ^ nxt
        prv = nxt

print("Finished. Time:", time.strftime("%c"))
print("Total:", total)

$ python2.7 test.py
Numbers: 100 69 38 24 17 11 3 22
Starting read. Time: Fri Feb  3 19:20:32 2017
Finished. Time: Fri Feb  3 19:21:36 2017
Total: 2603999886

%timeit numpy.fromfile('numbers.txt', dtype=int, sep=' ')
1 loop, best of 3: 23.6 s per loop

%timeit numpy.fromfile('numbers.bin')
1 loop, best of 3: 2.55 s per loop

from itertools import tee, izip as zip
import re

def pairwise(iterable):
    a,b = tee(iterable)
    next(b,None)
    return zip(a,b)

def process_data(data):
    return sum( a^b for a,b in pairwise(data) )

def process_str_file_re(fname):
    exp = re.compile(r"d+")
    with open(fname,"rb") as archi:
        return process_data( int( data.group() ) for data in exp.finditer(archi.read()) )