In Octave, how do I specify that the solution to a matrix equation should be over integers?

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In Octave, how do I specify that the solution to a matrix equation should be 
over integers? I.e., Given matrix A, vectors x and b; Ax=b. Find vector 
x=A^(−1)b such that all its entries are integers. While I'm primarily concerned 
with Octave, your answer may alternatively consider Wolfram|Alpha, or any other 
software available with a free online interface. If discussing Wolfram|Alpha or 
other systems, please also explain how to load a sparse matrix, which is 
currently in row, col, value format (i.e., I would prefer to do minimal format 
conversions).