View Compilation Error

0_0_21358053_10133.cpp: In member function 'Matrix Matrix::operator*(const Matrix&) const':
0_0_21358053_10133.cpp:23:52: error: 'MOD' was not declared in this scope
    c.x[i][k] = (c.x[i][k] + x[i][j] * A.x[j][k]) % MOD;
                                                    ^