foo.cc: In function 'void input()':
foo.cc:26:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   26 | scanf("%d%d",&N,&M);
      | ~~~~~^~~~~~~~~~~~~~
foo.cc:30:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   30 | scanf("%d%d%d",&u,&v,&w);
      | ~~~~~^~~~~~~~~~~~~~~~~~~

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