B"It's been almost a week since Polycarp couldn't get rid of insomnia. And as you may already know, one week in Berland lasts k days! When Polycarp went to a doctor with his problem, the doctor asked him about his sleeping schedule (more specifically, the average amount of hours of sleep per week). Luckily, Polycarp kept records of sleep times for the last n days. So now he has a sequence a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89an, where ai is the sleep time on the i-th day. The number of records is so large that Polycarp is unable to calculate the average value by himself. Thus he is asking you to help him with the calculations. To get the average Polycarp is going to consider k consecutive days as a week. So there will be n xe2 x80 x89- xe2 x80 x89k xe2 x80 x89+ xe2 x80 x891 weeks to take into consideration. For example, if k xe2 x80 x89= xe2 x80 x892, n xe2 x80 x89= xe2 x80 x893 and a xe2 x80 x89= xe2 x80 x89[3, xe2 x80 x894, xe2 x80 x897], then the result is . You should write a program which will calculate average sleep times of Polycarp over all weeks. The first line contains two integer numbers n and k (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89k xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x892 xc2 xb7105). The second line contains n integer numbers a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89an (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89ai xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89105). Output average sleeping time over all weeks. The answer is considered to be correct if its absolute or relative error does not exceed 10 xe2 x80 x89- xe2 x80 x896. In particular, it is enough to output real number with at least 6 digits after the decimal point. In the third example there are n xe2 x80 x89- xe2 x80 x89k xe2 x80 x89+ xe2 x80 x891 xe2 x80 x89= xe2 x80 x897 weeks, so the answer is sums of all weeks divided by 7. "...