Getting bored was never an option for Debu. So to keep himself occupied Debu asked his brother Biswa to find the sum of elements in a subarray of an array. But then it was too boring to begin with and hence Biswa asked Debu to find the Fibo-sum of a subarray.
But Debu was able to find the Fibo-sum of any subarray very easily so Biswa from time to time changed some element of the array to some other value and then continued asking him the Fibo-sum for different subarrays.