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 C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Math;

class Program
{
    static void Main()
    {
        var NQ = ReadLine().Split().Select(int.Parse).ToArray();
        var N = NQ[0];
        var Q = NQ[1];
        var bit =  new RangeSumBIT(N);
        for (int i = 0; i < Q; i++)
        {
            var line = ReadLine().Split().Select(int.Parse).ToArray();
            if (line[0] == 0) bit.Add(line[1] - 1, line[2]);
            else
            {
                WriteLine(bit.Sum(line[2]) - bit.Sum(line[1]-1));
            }
        }
    }
}

public class RangeSumBIT
{
    int N;
    int[] buffer;

    public RangeSumBIT(int size)
    {
        N = size;
        buffer = new int[size + 1];
    }

    public void Add(int index, int value)
    {
        for (int i = index + 1; i <= N; i += i & -i) buffer[i] += value;
    }

    public int Sum(int index)//[0,index)
    {
        int ret = 0;
        for (int i = index; i > 0; i -= i & -i) ret += buffer[i];
        return ret;
    }
}