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.IO;

namespace DSL2_B
{
    class BIT
    {
        internal int n;
        internal int[] bit;

        public BIT(int N)
        {
            n = N;
            bit = new int[n + 1];
        }

        public int Sum(int i)
        {
            int s = 0;
            while (i > 0)
            {
                s += bit[i];
                i -= i & -i;
            }
            return s;
        }

        public void Add(int i, int x)
        {
            while (i <= n)
            {
                bit[i] += x;
                i += i & -i;
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);
            var t = scan;
            int n = t[0]; int q = t[1];
            var B = new BIT(n);
            for (int i = 0; i < q; i++)
            {
                t = scan;
                if (t[0] == 0)
                {
                    B.Add(t[1], t[2]);
                }
                else
                {
                    Console.WriteLine(B.Sum(t[2]) - B.Sum(t[1] - 1));
                }
            }
            Console.Out.Flush();
        }

        static int[] scan { get { return Array.ConvertAll(Console.ReadLine().Split(), int.Parse); } }
    }
}