Concatenate cell array of different size along different index of cell

I want to concatenate cell array a{1,1}= 20x14 double matrix and a{1,2} = 30X50 double matrix by using cat(3,a{:}) but the error dimension of matrix

being concatenate is not consistent is coming

Please note i want to concatenate it in different index and not horizontal or vertical concat

[madhan ravi]

what's your desired final matrix size? suspect reshape has to be implied here