Еще одна старая задача, не помню условие, но есть решение на Python

gistfile1.py

from decimal import Decimal, ROUND_HALF_UP
import logging

logging.basicConfig(level=logging.DEBUG)

# Constants for rounding
TWO_DIGITS_ROUND = Decimal("0.01")
SIX_DIGITS_ROUND = Decimal("0.000001")

result_lst = []
# Number of crawfish we want to sell.
# By the condition, we sell a crawfish in a day. It means that if we want to
# sell less than i crawfish (i < 7), we will sell them i days and (7 - i) days
# we do nothing.
crawfish_num = Decimal(7).quantize(TWO_DIGITS_ROUND)

# Cost of 'weekly pack' of crawfish
crawfish_cost = Decimal(1.02).quantize(TWO_DIGITS_ROUND)

# Out balance to Ith day
balance = Decimal(0)

# Collected amount of money to Ith day

for i in range(1, crawfish_num + 1): # For every day
   i = Decimal(i)

   expected = i * (crawfish_cost / crawfish_num)
   expected = expected.quantize(TWO_DIGITS_ROUND, ROUND_HALF_UP)

   today_collected = (expected - sum(result_lst))
   result_lst.append(today_collected)


print 'Result:', result_lst, 'sum:', sum(result_lst)