Problem:
Range Sum Query

Write a program which manipulates a sequence A = {a1, a2, . . . , an} with the following operations:

add(i, x): add x to ai.

getSum(s, t): print the sum of as, as+1,...,at.

Note that the initial values of ai (i = 1, 2, . . . , n) are 0.

Input

n q
com1 x1 y1
com2 x2 y2
...
comq xq yq

In the first line, n (the number of elements in A) and q (the number of queries) are given. Then, q queries are given where com represents the type of queries. '0' denotes add(xi, yi) and '1' denotes getSum(xi, yi).

Output

For each getSum operation, print the sum in a line.

Constraints

1 ≤ n ≤ 100000

1 ≤ q ≤ 100000

If comi is 0, then 1 ≤ xi ≤ n, 0 ≤ yi ≤ 1000.

If comi is 1, then 1 ≤ xi ≤ n, 1 ≤ yi ≤ n.

Sample Input 1

3 5
0 1 1
0 2 2
0 3 3
1 1 2
1 2 2

Sample Output 1

3
2

Solution in OCaml (judge verdict: Accepted)

let split str delim =
  let open String in
  let rec doit s acc =
    match
      try Some (rindex s delim) with _ -> None
    with
    | None -> s :: acc
    | Some i -> doit (sub s 0 i) (sub s (i + 1) (length s - i - 1) :: acc) in
  doit str []

let parent i = int_of_float ((float_of_int (i - 1)) /. 2.)

let left i = 2*i + 1

let right i = 2*i + 2

let to_pow_of_2 n =
  let rec doit i =
    if i > n then i
    else doit (i * 2) in
  doit 1

let add (s : int array) n i x =
  let j = n + i - 1 in
  s.(j) <- x + s.(j);
  let rec doit j =
    if j > 0 then begin
      let j = parent j in
      s.(j) <- s.(left j) + s.(right j);
      doit j
    end in
  doit j

let sum s n a b =
  let rec doit a b k l r =
    if r < a || b < l then 0
    else if a <= l && r <= b then s.(k)
    else doit a b (left k) l ((l + r) / 2) + doit a b (right k) ((l + r) / 2 + 1) r in
  doit a b 0 0 (n - 1)

let solve n q =
  let n = to_pow_of_2 n in
  let s = Array.make (2*n) 0 in
  let rec doit i =
    if i < q then begin
      begin match List.map int_of_string (split (read_line ()) ' ') with
      | 0 :: x :: y :: _ -> add s n x y
      | 1 :: x :: y :: _ -> Printf.printf "%d\n" (sum s n x y)
      | _ -> ()
      end;
      doit (i + 1)
    end in
  doit 0

let () =
  match List.map int_of_string (split (read_line ()) ' ') with
  | [n; q] -> solve n q
  | _ -> ()