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)

#include <stdio.h>          // printf(), scanf()
#define MAX_N 100000

int bit[MAX_N + 1];
int n;

void
bit_init()
{
	int i;

	for (i = 0; i <= n; ++i)
		bit[i] = 0;
}

void
bit_add(int i, int v)
{
	while (i <= n)
	{
		bit[i] += v;
		i += i & -i;
	}
}

int
bit_sum(int i)
{
	int sum = 0;
	while (i > 0)
	{
		sum += bit[i];
		i -= i & -i;
	}

	return sum;
}

int
main(int argc, char** argv)
{
	int q;
	int c, x, y;

	scanf("%d %d", &n, &q);
	bit_init();
	while (q--)
	{
		scanf("%d %d %d", &c, &x, &y);
		if (c == 0)
			bit_add(x, y);
		else
			printf("%d\n", bit_sum(y) - bit_sum(x - 1));
	}

	return 0;
}