gen_input will genearte the input matrix with given dimension. Running it in
following way:

./gen_input [matrix_dimension]

e.g.:
./gen_input 32
will generate the input matrix of 32x32. The ouput contains three files:
${matrix_dim}.dat, l-${matrix_dim}.dat, u-${matrix_dim}.dat. In the above
example, the output should be 32.dat, l-32.dat, u-32.dat .
