Hexagon and rhombic domino

Hexagon with side n is divided into 6n^2 equilateral triangles with side 1.

In how many ways it can be covered by rhombic dominoes (without overlaps and goes beyond the border)?

(Orthorhombic domino consists of two equilateral triangles of side 1, adjacent to the side.)

Input

In the input file contains the number n (1 ≤ n ≤ 7).

Output

Display the number of tilings of a hexagon.

Examples