class NumArray {

    int[] map;
    public NumArray(int[] nums) {
        int sum = 0;
        map = new int[nums.length + 1];
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            map[i+1] = sum;
        }
    }

    public int sumRange(int i, int j) {
        if (map == null)
            return 0;


        return map[j + 1] - map[i];
    }
}