foo.cc: In function 'int main()':
foo.cc:5:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("landing.in.txt","r",stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:6:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("landing.out.txt","w",stdout);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:17:7: warning: 't' may be used uninitialized in this function [-Wmaybe-uninitialized]
       if(a[1][j]==t)
       ^~

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