1// get cumulative sum up to and including i
 2int Get(int i) {
 3  int res = 0;
 4  while(i) {
 5    res += B[i];
 6    i -= (i & -i);
 7  }
 8  return res;
 9}
10
11// add val to value at i
12void Set(int i, int val) {
13  while(i <= N) {
14    B[i] += val;
15    i += (i & -i);
16  }
17}