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 Ruby (judge verdict: Runtime Error)

class SegmentTree

  def initialize xs, id, &block
    @id = id
    @block = block
    i = 1
    i *= 2 while i < xs.size
    @width = i
    @data = Array.new(2 * i - 1, id)
    @data[i-1...i-1+xs.size] = xs
    (i-2).downto(0) {|j| @data[j] = block[@data[2*j+1], @data[2*j+2]] }
  end

  def query i, j, k = 0, a = 0, b = @width
    return @data[k] if i == a && j == b
    c = (a + b) / 2
    case
    when j <= c
      query i, j, 2 * k + 1, a, c
    when c <= i
      query i, j, 2 * k + 2, c, b
    else
      @block[query(i, c, 2 * k + 1, a, c), query(c, j, 2 * k + 2, c, b)]
    end
  end

  def [] i
    @data[@width - 1 + i]
  end

  def []= i, x
    i = @width - 1 + i
    @data[i] = x
    while i > 0
      j = (i-1)/2
      @data[j] = @block[@data[2*j+1], @data[2*j+2]]
      i = j
    end
  end

end

n, q = gets.split.map(&:to_i)
st = SegmentTree.new(Array.new(n, 0), 0) {|a, b| a + b }
q.times do
  c, x, y = gets.split.map(&:to_i)
  if c.zero?
    st[x] += y
  else
    p st.query x, y + 1
  end
end