foo.cc: In function 'int main()':
foo.cc:20:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   20 |     scanf("%d%d%d%d",&n,&m,&c1,&c2);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:22:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |         scanf("%d",&wei[i]);
      |         ~~~~~^~~~~~~~~~~~~~
foo.cc:28:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   28 |         scanf("%d%d%d",&a,&b,&c);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~

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