View Compilation Error

0_0_16891925_28255.cpp: In function 'Matrix Multiply(Matrix, Matrix)':
0_0_16891925_28255.cpp:24:76: error: 'mod' was not declared in this scope
                 ans.data[i][j]=(ans.data[i][j]+a.data[i][k]*b.data[k][j])%(mod-1);
                                                                            ^