foo.cc: In function 'int main()':
foo.cc:6:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    6 |  freopen("b.in","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:7:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    7 |  freopen("b.out","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~
foo.cc:18:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   18 |   scanf("%lld",&t);
      |   ~~~~~^~~~~~~~~~~

Found 10 testcases.