View Compilation Error

0_0_36613148_27759.cpp: In function 'int main()':
0_0_36613148_27759.cpp:17:22: error: 'j' was not declared in this scope
    long long bt=b[1]-j*a1[1];
                      ^
0_0_36613148_27759.cpp:17:24: error: 'a1' was not declared in this scope
    long long bt=b[1]-j*a1[1];
                        ^