Buggy python submission (verdict: Runtime Error):
import sys
import math
A, B = map(int, input().split())
if A == B:
  print (A)
  sys.exit()

def xor(a, b):
  r = ""
  for i in range(len(a)):
    if a[i] == "0" and b[i] == "0" or a[i] == "1" and b[i] == "1":
      r += "0"
    else:
      r += "1"
  return r

S = "0" * 50
def xorn(S, n):
  m = int(math.log2(n))
  b = n - 2 ** m
#  print (S[0:-m-1],1,S[-m-1:-1],m,b)
  S = S[0:-m-1] + "1" + S[-m-1:-1]
  if b == 0:
    return S
  return xorn(S, b)

s = int("0b" + xor(xorn(S, A-1), xorn(S, B)), 0)
print (s+1 if (B-A) % 2 == 1 else s)

Fixed submission:
import sys
import math
A, B = map(int, input().split())

def nXor(n):
  if n % 2 == 0:
    if (n//2) % 2 == 0:
      return 0 ^ n
    else:
      return 1 ^ n
  else:
    if ((n+1)//2) % 2 == 0:
      return 0
    else:
      return 1
n = 0
for i in range(9):
  n = n^i
print (nXor(A-1) ^ nXor(B))

Buggy python submission (verdict: Runtime Error):
import sys
import math
A, B = map(int, input().split())
if A == B:
  print (A)
  sys.exit()

def xor(a, b):
  r = ""
  for i in range(len(a)):
    if a[i] == "0" and b[i] == "0" or a[i] == "1" and b[i] == "1":
      r += "0"
    else:
      r += "1"
  return r

S = "0" * 50
def xorn(S, n):
  m = int(math.log2(n))
  b = n - 2 ** m
#  print (S[0:-m-1],1,S[-m-1:-1],m,b)
  S = S[0:-m-1] + "1" + S[-m-1:-1]
  if b == 0:
    return S
  return xorn(S, b)

print (int("0b" + xor(xorn(S, A), xorn(S, B)), 0))

Fixed submission:
import sys
import math
A, B = map(int, input().split())

def nXor(n):
  if n % 2 == 0:
    if (n//2) % 2 == 0:
      return 0 ^ n
    else:
      return 1 ^ n
  else:
    if ((n+1)//2) % 2 == 0:
      return 0
    else:
      return 1
n = 0
for i in range(9):
  n = n^i
print (nXor(A-1) ^ nXor(B))

Buggy python submission (verdict: Runtime Error):
import sys
import math
A, B = map(int, input().split())
if A == B:
  print (A)
  sys.exit()

def xor(a, b):
  r = ""
  for i in range(len(a)):
    if a[i] == "0" and b[i] == "0" or a[i] == "1" and b[i] == "1":
      r += "0"
    else:
      r += "1"
  return r

S = "0" * 40
def xorn(S, n):
  m = int(math.log2(n))
  b = n - 2 ** m
#  print (S[0:-m-1],1,S[-m-1:-1],m,b)
  S = S[0:-m-1] + "1" + S[-m-1:-1]
  if b == 0:
    return S
  return xorn(S, b)

print (int("0b" + xor(xorn(S, A-1), xorn(S, B)), 0))

Fixed submission:
import sys
import math
A, B = map(int, input().split())

def nXor(n):
  if n % 2 == 0:
    if (n//2) % 2 == 0:
      return 0 ^ n
    else:
      return 1 ^ n
  else:
    if ((n+1)//2) % 2 == 0:
      return 0
    else:
      return 1
n = 0
for i in range(9):
  n = n^i
print (nXor(A-1) ^ nXor(B))

Buggy python submission (verdict: Runtime Error):
import sys
import math
A, B = map(int, input().split())
if A == B:
  print (A)
  sys.exit()

def xor(a, b):
  r = ""
  for i in range(len(a)):
    if a[i] == "0" and b[i] == "0" or a[i] == "1" and b[i] == "1":
      r += "0"
    else:
      r += "1"
  return r

S = "0" * 10
def xorn(S, n):
  m = int(math.log2(n))
  b = n - 2 ** m
#  print (S[0:-m-1],1,S[-m-1:-1],m,b)
  S = S[0:-m-1] + "1" + S[-m-1:-1]
  if b == 0:
    return S
  return xorn(S, b)

print (int("0b" + xor(xorn(S, A-1), xorn(S, B)), 0))

Fixed submission:
import sys
import math
A, B = map(int, input().split())

def nXor(n):
  if n % 2 == 0:
    if (n//2) % 2 == 0:
      return 0 ^ n
    else:
      return 1 ^ n
  else:
    if ((n+1)//2) % 2 == 0:
      return 0
    else:
      return 1
n = 0
for i in range(9):
  n = n^i
print (nXor(A-1) ^ nXor(B))

Buggy python submission (verdict: Time Limit Exceeded):
A, B = map(int, input().split())
L = ["0" * (len(bin(B))-len(bin(x))) + bin(x)[2:] for x in range(A, B+1)]

def xor(a, b):
  r = ""
  for i in range(len(a)):
    if a[i] == "0" and b[i] == "0" or a[i] == "1" and b[i] == "1":
      r += "0"
    else:
      r += "1"
  return r

ans = L.pop()
while L:
#  print (ans)
  ans = xor(ans, L.pop())
print (int("0b" + ans, 0))

Fixed submission:
import sys
import math
A, B = map(int, input().split())

def nXor(n):
  if n % 2 == 0:
    if (n//2) % 2 == 0:
      return 0 ^ n
    else:
      return 1 ^ n
  else:
    if ((n+1)//2) % 2 == 0:
      return 0
    else:
      return 1
n = 0
for i in range(9):
  n = n^i
print (nXor(A-1) ^ nXor(B))