answer.code: In constructor ‘matrix::matrix()’:
answer.code:39:20: error: ‘memset’ was not declared in this scope
   39 |         matrix() { memset(a, 0, sizeof a); }
      |                    ^~~~~~
answer.code:6:1: note: ‘memset’ is defined in header ‘<cstring>’; did you forget to ‘#include <cstring>’?
    5 | #include <vector>
  +++ |+#include <cstring>
    6 | using namespace std;
answer.code: In function ‘int main()’:
answer.code:54:17: error: ‘memset’ was not declared in this scope
   54 |                 memset(a, 0, sizeof a);
      |                 ^~~~~~
answer.code:54:17: note: ‘memset’ is defined in header ‘<cstring>’; did you forget to ‘#include <cstring>’?
answer.code:69:17: error: ‘memset’ was not declared in this scope
   69 |                 memset(A, 0, sizeof A);
      |                 ^~~~~~
answer.code:69:17: note: ‘memset’ is defined in header ‘<cstring>’; did you forget to ‘#include <cstring>’?
answer.code:76:25: error: ‘memcpy’ was not declared in this scope
   76 |                         memcpy(A, B, sizeof B);
      |                         ^~~~~~
answer.code:76:25: note: ‘memcpy’ is defined in header ‘<cstring>’; did you forget to ‘#include <cstring>’?
answer.code:65:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   65 |         scanf("%d", &t);
      |         ~~~~~^~~~~~~~~~
answer.code:68:22: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   68 |                 scanf("%lld", &n);
      |                 ~~~~~^~~~~~~~~~~~