Bone for the Sharik

— Pechkin you will ever think?

— Why do I think? Let your Burenka thinks - her head is big ...

— Matroskin, what are you out there think?

— Why, I can not calculate how much you owe Sharik seed yield ... You had promised him a reward royally: the first cell of a chessboard the size N x N single bone, the second - two - the third four, and so on, so e. for each next cell twice. So I think what you have to seed Sharik bring ...

Help Matroskin count how many seeds should bring Pechkin.

Прослухати

Читати фонетично

Input

One number - the size of the chessboard N (1 ≤ N ≤ 100).

Output

Single number - the required amount of seed.

Examples