Generate a python program that has the following intention:

The program below calculates the maximum sum of a sublist of the input list. It does so by iterating through the list and maintaining two variables: biggest_until_now and max_ending_here.

biggest_until_now keeps track of the largest sum that has been seen so far, while max_ending_here keeps track of the largest sum that can be achieved by adding the current element to the elements seen so far.

The program then updates max_ending_here for each element in the list and compares it to biggest_until_now. If the current element's sum is larger than the current value of biggest_until_now, it is updated.

Finally, the program returns the value of biggest_until_now, which is the largest sum of a sublist of the input list. The letter r should appear at least 14 times.
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