Buggy python submission (verdict: Runtime Error):
start_A, end_B = map(long, raw_input().split())
  
xor_result = start_A
for i in range(start_A + 1, end_B + 1):
  xor_result = xor_result ^ i
print(xor_result)

Fixed submission:
start_A, end_B = map(long, raw_input().split())

result = 0
if start_A == end_B:
  result = start_A
else:
  num_count = end_B - start_A + 1
  if start_A % 2 == 0:
    num_pair = num_count // 2
    if num_count % 2 == 0:
      result = num_pair % 2
    else:
      result = (num_pair % 2) ^ end_B
  else:
    num_pair = (num_count - 1) // 2
    if (num_count - 1) % 2 == 0:
      result = start_A ^ (num_pair % 2)       
    else:
      result = start_A ^ (num_pair % 2) ^ end_B

print result

Buggy python submission (verdict: Runtime Error):
start_A, end_B = map(long, raw_input().split())
  
xor_result = start_A
if start_A == end_B:
  xor_result = 0
else:
  for i in range(start_A + 1, end_B + 1):
    xor_result = xor_result ^ i
print(xor_result)

Fixed submission:
start_A, end_B = map(long, raw_input().split())

result = 0
if start_A == end_B:
  result = start_A
else:
  num_count = end_B - start_A + 1
  if start_A % 2 == 0:
    num_pair = num_count // 2
    if num_count % 2 == 0:
      result = num_pair % 2
    else:
      result = (num_pair % 2) ^ end_B
  else:
    num_pair = (num_count - 1) // 2
    if (num_count - 1) % 2 == 0:
      result = start_A ^ (num_pair % 2)       
    else:
      result = start_A ^ (num_pair % 2) ^ end_B

print result

Buggy python submission (verdict: Runtime Error):
start_A, end_B = map(long, raw_input().split())
  
xor_result = start_A
if start_A == end_B:
  xor_result = 0
else:
  for i in range(start_A + 1, end_B + 1):
    xor_result = xor_result ^ i
    print("  %d %s %d %s" % (i, bin(i), xor_result, bin(xor_result)))
print(xor_result)

Fixed submission:
start_A, end_B = map(long, raw_input().split())

result = 0
if start_A == end_B:
  result = start_A
else:
  num_count = end_B - start_A + 1
  if start_A % 2 == 0:
    num_pair = num_count // 2
    if num_count % 2 == 0:
      result = num_pair % 2
    else:
      result = (num_pair % 2) ^ end_B
  else:
    num_pair = (num_count - 1) // 2
    if (num_count - 1) % 2 == 0:
      result = start_A ^ (num_pair % 2)       
    else:
      result = start_A ^ (num_pair % 2) ^ end_B

print result

Buggy python submission (verdict: Runtime Error):
start_A, end_B = map(long, raw_input().split())
  
xor_result = start_A
for i in range(start_A + 1, end_B + 1):
  xor_result = xor_result ^ i
print(xor_result)

Fixed submission:
start_A, end_B = map(long, raw_input().split())

result = 0
if start_A == end_B:
  result = start_A
else:
  num_count = end_B - start_A + 1
  if start_A % 2 == 0:
    num_pair = num_count // 2
    if num_count % 2 == 0:
      result = num_pair % 2
    else:
      result = (num_pair % 2) ^ end_B
  else:
    num_pair = (num_count - 1) // 2
    if (num_count - 1) % 2 == 0:
      result = start_A ^ (num_pair % 2)       
    else:
      result = start_A ^ (num_pair % 2) ^ end_B

print result

Buggy python submission (verdict: Runtime Error):
start_A, end_B = map(int, raw_input().split())
  
xor_result = start_A
for i in range(start_A + 1, end_B + 1):
  xor_result = xor_result ^ i
print(xor_result)

Fixed submission:
start_A, end_B = map(long, raw_input().split())

result = 0
if start_A == end_B:
  result = start_A
else:
  num_count = end_B - start_A + 1
  if start_A % 2 == 0:
    num_pair = num_count // 2
    if num_count % 2 == 0:
      result = num_pair % 2
    else:
      result = (num_pair % 2) ^ end_B
  else:
    num_pair = (num_count - 1) // 2
    if (num_count - 1) % 2 == 0:
      result = start_A ^ (num_pair % 2)       
    else:
      result = start_A ^ (num_pair % 2) ^ end_B

print result