numbers = [2,3,4,11,7,77,8,34,56,21,10, 20, 4, 45, 99]
sums = [0] * (len(numbers)+1)

First create a prefix sum Array

for i in range(len(numbers)):
sums[i+1] = sums[i] + numbers[i]

print(sums)

Second find a sum of numbers in a given range

rangeSum = sums[11] - sums[5]
print(rangeSum)