For example, some company need to pay 1500000$ taxes, but it paid only 500000$, and we need to calculate penalty. Last tax payment was 100 days ago and penalti calculation uses refinancing rate of RF main Bank. Refinancing rate changes over time, and in last 100 days it, for example, changed 5 times. We need count how many days with every refinancing rate, and calculate final sum of taxes + penalti.