# Finding hill cipher key

I have the plaintext

ｂｒｅａｔｈｔａｋｉｎｇ

Which encrypts to the cipher text

ＲＵＰＯＴＥＮＴＯＩＦＶ

I know that it was encrypted with a hill cipher
(m not specified) but I have no clue what i'm
doing wrong trying to decipher the text.

I set up the vectors for the plaintext
m1 = (1,17,4)
m2=(0,19,7)
m3=(19,0,10)

And the vectors for the ciphertext
c1 = (17,20,16)
c2 = (14,19,4)
c3 = (13,19,14)

I know to solve for K (the key matrix) in (mod 26)
I need to solve K * M = C
Where M is the matrix of the plaintext in (mod 26)
and C is the matrix w/ the ciphertext in (mod 26)

So, I start off by trying to find the inverse of the
plaintext matrix

\begin{bmatrix} 1 & 0 & 19 \\ 17 & 19 & 0 \\ 4 & 7 & 10 \\ \end{bmatrix}

But I end up gettng 13 and 13 doesn't have an inverse
mod 26.. So I have no idea how to solve this.