View Compilation Error

0_0_25811301_12782.cpp: In function 'Matrix mul(Matrix, Matrix)':
0_0_25811301_12782.cpp:25:33: error: 'mod' was not declared in this scope
                 temp.t[i][j] %= mod;
                                 ^
0_0_25811301_12782.cpp: In function 'int main()':
0_0_25811301_12782.cpp:62:43: error: 'mod' was not declared in this scope
             Matrix r = fpow_mod(ans,n - 4,mod);
                                           ^