As you know, the cat Matroskin is very proud of his cow Murka. He is especially proud of Murka's calves. Over the past n years, cow Murka has had one calf. At birth, a calf weighs one kilogram. Each year, each calf gains two kilograms. The pride of the Matroskin cat will be the greater, the greater the average weight of the calf. After the birth of another calf this year, Matroskin decided to find out the extent of his pride.
Help Matroskin find out the level of his pride, that is, find the average weight of all calves born over n years.
Input
A single integer is entered 1<=n<=1000 — the number of years that Murka had calves.
Imprint
Output the average weight of all born calves.
Examples