I try to make calculation with matrix in matix for example

n1 >0 , n2 >0; n1 ,n2 unknow
matirx  A11 := matrix(n1,n1,[unknow variables ]);
matirx  A12 := matrix(n1,n2,[unknow variables ]);
matirx  A21 := matrix(n2,n1,[unknow variables ]);
matirx  A22 := matrix(n2,n2,[unknow variables ]);

A_big := matrix(n1+n2,n1+n2 , [[A11,A12],[A21,A22]]);

how i will sovle

A_big ^ (-1) ;

The wrong answer is
matrix(...