In mathematics, particularly in linear algebra,
a skew-symmetric matrix(also known as an antisymmetric or antimetric) is a square matrix **A** whose transpose
is also its negative.
This means it satisfies the equation
A = −A^{T}.
If the entry in the i-th row and j-th column is a_{ij}, i.e.
A = (a_{ij})
then the symmetric condition becomes
a_{ij} = −a_{ji}.

You should determine whether the specified square matrix is skew-symmetric or not.

You can find more details on Skew-symmetric matrices on its Wikipedia page.

**Input: ** A square matrix as a list of lists with integers.

**Output: ** If the matrix is skew-symmetric or not as a boolean.

**Example:**

checkio([ [ 0, 1, 2], [-1, 0, 1], [-2, -1, 0]]) == True checkio([ [ 0, 1, 2], [-1, 1, 1], [-2, -1, 0]]) == False checkio([ [ 0, 1, 2], [-1, 0, 1], [-3, -1, 0]]) == False

**How it is used: **
Skew-symmetric matrices can be useful for the cross product, an operation in mathematics used in the calculation of movement of forces.
Matrixes are basis for the linear algebra and vector graphics.

**Precondition:** 0 < N < 5