evenSum to store the sum of even numbers in nums.nums and add all even numbers to evenSum.result to store the sum of even numbers after each query.queries and for each query:
a. Extract val and index from the query.
b. If nums[index] is even, subtract it from evenSum.
c. Update nums[index] by adding val to it.
d. If nums[index] is now even, add it to evenSum.
e. Append evenSum to result.result.