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Calculating the inverse modularity of the determinant for Hill cipher

I'm trying to decrypt a message encrypted with Hill Cipher, but I don't understand how to find the determinant so it solves the equation $det * 1/det = 1 mod 26$. The determinant for my key matrix is ...
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Why does my implementation of CBC mode only decrypt the first block correctly? [closed]

I have the following code that uses a CBC mode to encrypt a text by dividing it to 3-elements block. But it only works correctly on the first block which is xored with the IV. ...