# Lucky Five

Pine forest. Pine Forest in the Vyatka province. 1872. Kramskoy, each artist wrote of the "Pine forests", emphasizing full-scale accuracy of image: "The forest is wild and creek with glandular, dark-yellow water, which shows the entire bottom strewn with stones ..."However, it should be noted that at its Shishkin canvas several theatrical and forest landscape, offering a "spectacle of nature."

Some people feel lucky number five. They throw a few bones, and if five drops more than one fifth of the bone, then the day is considered lucky.

Throws dice the same bones, having the sides of the parties. Necessary to calculate the probability that the day will be happy. The probability of getting five at throwing dice with sides sides equal to 1 / sides.

## Input

Each line is a separate test and contains the number of rolls the dice (1 ≤ dice ≤ 20) and the number of sides (5 ≤ sides ≤ 10) in them. Output

For each test on a separate line to derive the probability that the day will be happy. Probability output of 6 characters after the decimal point.