Range Updates and Range Queries with BIT

Range Updates and Range Queries.py

update(ft, p, v):
  for (; p <= N; p += p&(-p))
    ft[p] += v 	 

# Add v to A[a...b] 
update(a, b, v): 	
  update(B1, a, v) 	
  update(B1, b + 1, -v) 	
  update(B2, a, v * (a-1)) 	
  update(B2, b + 1, -v * b) 	 

query(ft, b): 	
  sum = 0 	
  for(; b > 0; b -= b&(-b))
    sum += ft[b]
  return sum

# Return sum A[1...b]
query(b):
  return query(B1, b) * b - query(B2, b)

# Return sum A[a...b]
query(a, b):
  return query(b) - query(a-1)

I suppose there should be 'b' instead of 'j' in line 10.