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var NumArray = function (nums) {
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  this.nums = nums;
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  this.n = nums.length;
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  this.fenwickTree = new Array(this.n + 1).fill(0);
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  nums.forEach((num, index) => this.init(index, num));
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};
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NumArray.prototype.init = function (index, val) {
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  let j = index + 1;
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  while (j <= this.n) {
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    this.fenwickTree[j] += val;
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    j += this.lsb(j);
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  }
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};
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NumArray.prototype.lsb = function (index) {
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  return index & ~(index - 1);
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};
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NumArray.prototype.update = function (index, val) {
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  const diff = val - this.nums[index];
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  this.nums[index] = val;
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  this.init(index, diff);
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};
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NumArray.prototype.getSum = function (index) {
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  let j = index + 1;
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  let sum = 0;
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  while (j > 0) {
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    sum += this.fenwickTree[j];
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    j -= this.lsb(j);
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  }
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  return sum;
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};
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NumArray.prototype.sumRange = function (left, right) {
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  return this.getSum(right) - this.getSum(left - 1);
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};