foo.cc: In function 'void init()':
foo.cc:18:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:20:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&have[i]);
   ~~~~~^~~~~~~~~~~~~~~
foo.cc:23:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&m);
  ~~~~~^~~~~~~~~
foo.cc:25:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&need[i]);
   ~~~~~^~~~~~~~~~~~~~~

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