This code is supposed to ask user max number of elements (n) for square matrix and elements of that same matrix (m).
I used do-while loops for input n and for input of m dimensions. Range is set in while conditions.
With switch cases i made simple menu which you can switch and do 3 different operations with matrix that user has inputted.
First operation is calculating mean of secondary diagonal in specified matrix. Second operation is calculating sum of odd elements on first row and first column. If odd elements are non existent, program is printing that sum is zero and odd elements are not existing. Third operation is printing all numbers with even indexes(both indexes must be even).