View Compilation Error

0_0_17779220_29480.cpp: In function 'int solve(long long int (*)[1005], bool*, long long int*, const int&)':
0_0_17779220_29480.cpp:59:64: error: 'imul' was not declared in this scope
                     a[j][k] = ((a[j][k] /** jmul*/ - a[r][k] * imul) % mod + mod) % mod; //模方程组，模为7
                                                                ^